Aerodynamic shape optimization using control theory
Reuther, James
1996-01-01
Aerodynamic shape design has long persisted as a difficult scientific challenge due its highly nonlinear flow physics and daunting geometric complexity. However, with the emergence of Computational Fluid Dynamics (CFD) it has become possible to make accurate predictions of flows which are not dominated by viscous effects. It is thus worthwhile to explore the extension of CFD methods for flow analysis to the treatment of aerodynamic shape design. Two new aerodynamic shape design methods are developed which combine existing CFD technology, optimal control theory, and numerical optimization techniques. Flow analysis methods for the potential flow equation and the Euler equations form the basis of the two respective design methods. In each case, optimal control theory is used to derive the adjoint differential equations, the solution of which provides the necessary gradient information to a numerical optimization method much more efficiently then by conventional finite differencing. Each technique uses a quasi-Newton numerical optimization algorithm to drive an aerodynamic objective function toward a minimum. An analytic grid perturbation method is developed to modify body fitted meshes to accommodate shape changes during the design process. Both Hicks-Henne perturbation functions and B-spline control points are explored as suitable design variables. The new methods prove to be computationally efficient and robust, and can be used for practical airfoil design including geometric and aerodynamic constraints. Objective functions are chosen to allow both inverse design to a target pressure distribution and wave drag minimization. Several design cases are presented for each method illustrating its practicality and efficiency. These include non-lifting and lifting airfoils operating at both subsonic and transonic conditions.
Parameterization adaption for 3D shape optimization in aerodynamics
Directory of Open Access Journals (Sweden)
Badr Abou El Majd
2013-10-01
Full Text Available When solving a PDE problem numerically, a certain mesh-refinement process is always implicit, and very classically, mesh adaptivity is a very effective means to accelerate grid convergence. Similarly, when optimizing a shape by means of an explicit geometrical representation, it is natural to seek for an analogous concept of parameterization adaptivity. We propose here an adaptive parameterization for three-dimensional optimum design in aerodynamics by using the so-called “Free-Form Deformation” approach based on 3D tensorial Bézier parameterization. The proposed procedure leads to efficient numerical simulations with highly reduced computational costs.[How to cite this article: Majd, B.A.. 2014. Parameterization adaption for 3D shape optimization in aerodynamics. International Journal of Science and Engineering, 6(1:61-69. Doi: 10.12777/ijse.6.1.61-69
Shape optimization for aerodynamic efficiency and low observability
Vinh, Hoang; Van Dam, C. P.; Dwyer, Harry A.
1993-01-01
Field methods based on the finite-difference approximations of the time-domain Maxwell's equations and the potential-flow equation have been developed to solve the multidisciplinary problem of airfoil shaping for aerodynamic efficiency and low radar cross section (RCS). A parametric study and an optimization study employing the two analysis methods are presented to illustrate their combined capabilities. The parametric study shows that for frontal radar illumination, the RCS of an airfoil is independent of the chordwise location of maximum thickness but depends strongly on the maximum thickness, leading-edge radius, and leadingedge shape. In addition, this study shows that the RCS of an airfoil can be reduced without significant effects on its transonic aerodynamic efficiency by reducing the leading-edge radius and/or modifying the shape of the leading edge. The optimization study involves the minimization of wave drag for a non-lifting, symmetrical airfoil with constraints on the airfoil maximum thickness and monostatic RCS. This optimization study shows that the two analysis methods can be used effectively to design aerodynamically efficient airfoils with certain desired RCS characteristics.
Genetic Algorithms Applied to Multi-Objective Aerodynamic Shape Optimization
Holst, Terry L.
2005-01-01
A genetic algorithm approach suitable for solving multi-objective problems is described and evaluated using a series of aerodynamic shape optimization problems. Several new features including two variations of a binning selection algorithm and a gene-space transformation procedure are included. The genetic algorithm is suitable for finding Pareto optimal solutions in search spaces that are defined by any number of genes and that contain any number of local extrema. A new masking array capability is included allowing any gene or gene subset to be eliminated as decision variables from the design space. This allows determination of the effect of a single gene or gene subset on the Pareto optimal solution. Results indicate that the genetic algorithm optimization approach is flexible in application and reliable. The binning selection algorithms generally provide Pareto front quality enhancements and moderate convergence efficiency improvements for most of the problems solved.
Three dimensional large scale aerodynamic shape optimization based on shape calculus
Schmidt, Stephan; Gauger, Nicolas,; Ilic, Caslav; Schulz, Volker
2011-01-01
Large-scale three-dimensional aerodynamic shape optimization based on the compressible Euler equations is considered. Shape calculus is used to derive an exact surface formulation of the gradients, enabling the computation of shape gradient information for each surface mesh node without having to calculate further mesh sensitivities. Special attention is paid to the applicability to large-scale three dimensional problems like the optimization of an Onera M6 wing or a complete blended-wing–bod...
Aerodynamic Optimization of the Nose Shape of a Train Using the Adjoint Method
Directory of Open Access Journals (Sweden)
Jorge Munoz-Paniagua
2015-01-01
Full Text Available The adjoint method is used in this paper for the aerodynamic optimization of the nose shape of a train. This method has been extensively applied in aircraft or ground vehicle aerodynamic optimization, but is still in progress in train aerodynamics. Here we consider this innovative optimization method and present its application to reduce the aerodynamic drag when the train is subjected to front wind. The objective of this paper is to demonstrate the effectiveness of the method, highlighting the requirements, limitations and capabilities of it. Furthermore, a significant reduction of the aerodynamic drag in a short number of solver calls is aimed as well. The independence of the computational cost with respect to the number of design variables that define the optimal candidate is stressed as the most interesting characteristic of the adjoint method. This behavior permits a more complete modification of the shape of the train nose because the number of design variables is not a constraint anymore. The information obtained from the sensitivity field permits determining the regions of the geometry where a small modification of the nose shape might introduce a larger improvement of the train performance. A good agreement between this information and the successive geometry modifications is observed here.
Aerodynamic Shape Optimization Using A Real-Number-Encoded Genetic Algorithm
Holst, Terry L.; Pulliam, Thomas H.
2001-01-01
A new method for aerodynamic shape optimization using a genetic algorithm with real number encoding is presented. The algorithm is used to optimize three different problems, a simple hill climbing problem, a quasi-one-dimensional nozzle problem using an Euler equation solver and a three-dimensional transonic wing problem using a nonlinear potential solver. Results indicate that the genetic algorithm is easy to implement and extremely reliable, being relatively insensitive to design space noise.
Overview of Sensitivity Analysis and Shape Optimization for Complex Aerodynamic Configurations
Newman, Perry A.; Newman, James C., III; Barnwell, Richard W.; Taylor, Arthur C., III; Hou, Gene J.-W.
1998-01-01
This paper presents a brief overview of some of the more recent advances in steady aerodynamic shape-design sensitivity analysis and optimization, based on advanced computational fluid dynamics. The focus here is on those methods particularly well- suited to the study of geometrically complex configurations and their potentially complex associated flow physics. When nonlinear state equations are considered in the optimization process, difficulties are found in the application of sensitivity analysis. Some techniques for circumventing such difficulties are currently being explored and are included here. Attention is directed to methods that utilize automatic differentiation to obtain aerodynamic sensitivity derivatives for both complex configurations and complex flow physics. Various examples of shape-design sensitivity analysis for unstructured-grid computational fluid dynamics algorithms are demonstrated for different formulations of the sensitivity equations. Finally, the use of advanced, unstructured-grid computational fluid dynamics in multidisciplinary analyses and multidisciplinary sensitivity analyses within future optimization processes is recommended and encouraged.
Osusky, Lana Maria
The increase in the availability and power of computational resources over the last fifteen years has contributed to the development of many different types of numerical optimization methods and created a large area of research focussed on numerical aerodynamic shape optimization and, more recently, high-fidelity multidisciplinary optimization. Numerical optimization provides dramatic savings when designing new aerodynamic configurations, as it allows the designer to focus more on the development of a well-posed design problem rather than on performing an exhaustive search of the design space via the traditional cut-and-try approach, which is expensive and time-consuming. It also reduces the dependence on the designer's experience and intuition, which can potentially lead to more optimal designs. Numerical optimization methods are particularly attractive when designing novel, unconventional aircraft for which the designer has no pre-existing studies or experiences from which to draw; these methods have the potential to discover new designs that might never have been arrived at without optimization. This work presents an extension of an efficient gradient-based numerical aerodynamic shape optimization algorithm to enable optimization in turbulent flow. The algorithm includes an integrated geometry parameterization and mesh movement scheme, an efficient parallel Newton-Krylov-Schur algorithm for solving the Reynolds-Averaged Navier-Stokes (RANS) equations, which are fully coupled with the one-equation Spalart-Allmaras turbulence model, and a discrete-adjoint gradient evaluation. In order to develop an efficient methodology for optimization in turbulent flows, the viscous and turbulent terms in the ii governing equations were linearized by hand. Additionally, a set of mesh refinement tools was introduced in order to obtain both an acceptable control volume mesh and a sufficiently refined computational mesh from an initial coarse mesh. A series of drag minimization
Surrogate Based Optimization of Aerodynamic Noise for Streamlined Shape of High Speed Trains
Directory of Open Access Journals (Sweden)
Zhenxu Sun
2017-02-01
Full Text Available Aerodynamic noise increases with the sixth power of the running speed. As the speed increases, aerodynamic noise becomes predominant and begins to be the main noise source at a certain high speed. As a result, aerodynamic noise has to be focused on when designing new high-speed trains. In order to perform the aerodynamic noise optimization, the equivalent continuous sound pressure level (SPL has been used in the present paper, which could take all of the far field observation probes into consideration. The Non-Linear Acoustics Solver (NLAS approach has been utilized for acoustic calculation. With the use of Kriging surrogate model, a multi-objective optimization of the streamlined shape of high-speed trains has been performed, which takes the noise level in the far field and the drag of the whole train as the objectives. To efficiently construct the Kriging model, the cross validation approach has been adopted. Optimization results reveal that both the equivalent continuous sound pressure level and the drag of the whole train are reduced in a certain extent.
Directory of Open Access Journals (Sweden)
Kolář Jan
2012-04-01
Full Text Available The aerodynamic shape optimization of the supersonic flat nozzle is the aim of proposed paper. The nozzle discussed, is applied as a primary nozzle of the inlet part of supersonic wind tunnel. Supersonic nozzles of the measure area inlet parts need to guarantee several requirements of flow properties and quality. Mach number and minimal differences between real and required velocity and turbulence profiles at the nozzle exit are the most important parameters to meet. The aerodynamic shape optimization of the flat 2D nozzle in CFD is employed to reach as uniform exit velocity profile as possible, with the mean Mach number 1.4. Optimization process does not use any of standard routines of global or local optimum searching. Instead, newly formed routine, which exploits shape-based oriented sequence of nozzles, is used to research within whole discretized parametric space. The movement within optimization process is not driven by gradient or evolutionary too, instead, the Path of Minimal Shape Deformation is followed. Dynamic mesh approach is used to deform the shape and mesh from the actual nozzle to the subsequent one. Dynamic deformation of mesh allows to speed up whole converging process as an initialization of flow at the newly formed mesh is based on afore-computed shape. Shape-based similarity query in field of supersonic nozzles is discussed and applied. Evolutionary technique with genetic algorithm is used to search for minimal deformational path. As a result, the best variant from the set of solved shapes is analyzed at the base of momentum coefficient and desired Mach number at the nozzle exit.
Kolář, Jan
2012-04-01
The aerodynamic shape optimization of the supersonic flat nozzle is the aim of proposed paper. The nozzle discussed, is applied as a primary nozzle of the inlet part of supersonic wind tunnel. Supersonic nozzles of the measure area inlet parts need to guarantee several requirements of flow properties and quality. Mach number and minimal differences between real and required velocity and turbulence profiles at the nozzle exit are the most important parameters to meet. The aerodynamic shape optimization of the flat 2D nozzle in CFD is employed to reach as uniform exit velocity profile as possible, with the mean Mach number 1.4. Optimization process does not use any of standard routines of global or local optimum searching. Instead, newly formed routine, which exploits shape-based oriented sequence of nozzles, is used to research within whole discretized parametric space. The movement within optimization process is not driven by gradient or evolutionary too, instead, the Path of Minimal Shape Deformation is followed. Dynamic mesh approach is used to deform the shape and mesh from the actual nozzle to the subsequent one. Dynamic deformation of mesh allows to speed up whole converging process as an initialization of flow at the newly formed mesh is based on afore-computed shape. Shape-based similarity query in field of supersonic nozzles is discussed and applied. Evolutionary technique with genetic algorithm is used to search for minimal deformational path. As a result, the best variant from the set of solved shapes is analyzed at the base of momentum coefficient and desired Mach number at the nozzle exit.
Aerodynamic shape optimization of a HSCT type configuration with improved surface definition
Thomas, Almuttil M.; Tiwari, Surendra N.
1994-01-01
Two distinct parametrization procedures of generating free-form surfaces to represent aerospace vehicles are presented. The first procedure is the representation using spline functions such as nonuniform rational b-splines (NURBS) and the second is a novel (geometrical) parametrization using solutions to a suitably chosen partial differential equation. The main idea is to develop a surface which is more versatile and can be used in an optimization process. Unstructured volume grid is generated by an advancing front algorithm and solutions obtained using an Euler solver. Grid sensitivity with respect to surface design parameters and aerodynamic sensitivity coefficients based on potential flow is obtained using an automatic differentiator precompiler software tool. Aerodynamic shape optimization of a complete aircraft with twenty four design variables is performed. High speed civil transport aircraft (HSCT) configurations are targeted to demonstrate the process.
Brezillon, J.; Dwight, R.P.
2009-01-01
Within the next few years, numerical shape optimization based on high fidelity methods is likely to play a strategic role in future aircraft design. In this context, suitable tools have to be developed for solving aerodynamic shape optimization problems, and the adjoint approach - which allows fast
Taylor, Arthur C., III; Newman, James C., III; Barnwell, Richard W.
1997-01-01
A three-dimensional unstructured grid approach to aerodynamic shape sensitivity analysis and design optimization has been developed and is extended to model geometrically complex configurations. The advantage of unstructured grids (when compared with a structured-grid approach) is their inherent ability to discretize irregularly shaped domains with greater efficiency and less effort. Hence, this approach is ideally suited for geometrically complex configurations of practical interest. In this work the nonlinear Euler equations are solved using an upwind, cell-centered, finite-volume scheme. The discrete, linearized systems which result from this scheme are solved iteratively by a preconditioned conjugate-gradient-like algorithm known as GMRES for the two-dimensional geometry and a Gauss-Seidel algorithm for the three-dimensional; similar procedures are used to solve the accompanying linear aerodynamic sensitivity equations in incremental iterative form. As shown, this particular form of the sensitivity equation makes large-scale gradient-based aerodynamic optimization possible by taking advantage of memory efficient methods to construct exact Jacobian matrix-vector products. Simple parameterization techniques are utilized for demonstrative purposes. Once the surface has been deformed, the unstructured grid is adapted by considering the mesh as a system of interconnected springs. Grid sensitivities are obtained by differentiating the surface parameterization and the grid adaptation algorithms with ADIFOR (which is an advanced automatic-differentiation software tool). To demonstrate the ability of this procedure to analyze and design complex configurations of practical interest, the sensitivity analysis and shape optimization has been performed for a two-dimensional high-lift multielement airfoil and for a three-dimensional Boeing 747-200 aircraft.
Reuther, James; Jameson, Antony; Alonso, Juan Jose; Rimlinger, Mark J.; Saunders, David
1997-01-01
An aerodynamic shape optimization method that treats the design of complex aircraft configurations subject to high fidelity computational fluid dynamics (CFD), geometric constraints and multiple design points is described. The design process will be greatly accelerated through the use of both control theory and distributed memory computer architectures. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods. The resulting problem is implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on a higher order CFD method. In order to facilitate the integration of these high fidelity CFD approaches into future multi-disciplinary optimization (NW) applications, new methods must be developed which are capable of simultaneously addressing complex geometries, multiple objective functions, and geometric design constraints. In our earlier studies, we coupled the adjoint based design formulations with unconstrained optimization algorithms and showed that the approach was effective for the aerodynamic design of airfoils, wings, wing-bodies, and complex aircraft configurations. In many of the results presented in these earlier works, geometric constraints were satisfied either by a projection into feasible space or by posing the design space parameterization such that it automatically satisfied constraints. Furthermore, with the exception of reference 9 where the second author initially explored the use of multipoint design in conjunction with adjoint formulations, our earlier works have focused on single point design efforts. Here we demonstrate that the same methodology may be extended to treat
Efficient algorithms for future aircraft design: Contributions to aerodynamic shape optimization
Hicken, Jason Edward
Advances in numerical optimization have raised the possibility that efficient and novel aircraft configurations may be "discovered" by an algorithm. To begin exploring this possibility, a fast and robust set of tools for aerodynamic shape optimization is developed. Parameterization and mesh-movement are integrated to accommodate large changes in the geometry. This integrated approach uses a coarse B-spline control grid to represent the geometry and move the computational mesh; consequently, the mesh-movement algorithm is two to three orders faster than a node-based linear elasticity approach, without compromising mesh quality. Aerodynamic analysis is performed using a flow solver for the Euler equations. The governing equations are discretized using summation-by-parts finite-difference operators and simultaneous approximation terms, which permit C0 mesh continuity at block interfaces. The discretization results in a set of nonlinear algebraic equations, which are solved using an efficient parallel Newton-Krylov-Schur strategy. A gradient-based optimization algorithm is adopted. The gradient is evaluated using adjoint variables for the flow and mesh equations in a sequential approach. The flow adjoint equations are solved using a novel variant of the Krylov solver GCROT. This variant of GCROT is flexible to take advantage of non-stationary preconditioners and is shown to outperform restarted flexible GMRES. The aerodynamic optimizer is applied to several studies of induced-drag minimization. An elliptical lift distribution is recovered by varying spanwise twist, thereby validating the algorithm. Planform optimization based on the Euler equations produces a nonelliptical lift distribution, in contrast with the predictions of lifting-line theory. A study of spanwise vertical shape optimization confirms that a winglet-up configuration is more efficient than a winglet-down configuration. A split-tip geometry is used to explore nonlinear wake-wing interactions: the
Aerodynamically shaped vortex generators
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Velte, Clara Marika; Øye, Stig;
2016-01-01
An aerodynamically shaped vortex generator has been proposed, manufactured and tested in a wind tunnel. The effect on the overall performance when applied on a thick airfoil is an increased lift to drag ratio compared with standard vortex generators. Copyright © 2015 John Wiley & Sons, Ltd....
Brezillon, Joël; Dwight, Richard P.
2009-01-01
Within the next few years, numerical shape optimization based on high fidelity methods is likely to play a strategic role in future aircraft design. In this context, suitable tools have to be developed for solving aerodynamic shape optimization problems, and the adjoint approach - which allows fast and accurate evaluations of the gradients with respect to the design parameters - is seen as a promising strategy. After describing the theory of the viscous discrete adjoint method and its impleme...
Brezillon, J.; Dwight, R.P.
2009-01-01
Within the next few years, numerical shape optimization based on high fidelity methods is likely to play a strategic role in future aircraft design. In this context, suitable tools have to be developed for solving aerodynamic shape optimization problems, and the adjoint approach - which allows fast and accurate evaluations of the gradients with respect to the design parameters - is seen as a promising strategy. After describing the theory of the viscous discrete adjoint method and its impleme...
Reuther, James; Alonso, Juan Jose; Rimlinger, Mark J.; Jameson, Antony
1996-01-01
This work describes the application of a control theory-based aerodynamic shape optimization method to the problem of supersonic aircraft design. The design process is greatly accelerated through the use of both control theory and a parallel implementation on distributed memory computers. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods (13, 12, 44, 38). The resulting problem is then implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) Standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on higher order computational fluid dynamics methods (CFD). In our earlier studies, the serial implementation of this design method (19, 20, 21, 23, 39, 25, 40, 41, 42, 43, 9) was shown to be effective for the optimization of airfoils, wings, wing-bodies, and complex aircraft configurations using both the potential equation and the Euler equations (39, 25). In our most recent paper, the Euler method was extended to treat complete aircraft configurations via a new multiblock implementation. Furthermore, during the same conference, we also presented preliminary results demonstrating that the basic methodology could be ported to distributed memory parallel computing architectures [241. In this paper, our concem will be to demonstrate that the combined power of these new technologies can be used routinely in an industrial design environment by applying it to the case study of the design of typical supersonic transport configurations. A particular difficulty of this test case is posed by the propulsion/airframe integration.
Institute of Scientific and Technical Information of China (English)
刘洪
2004-01-01
A multiple-objective evolutionary algorithm (MOEA) with a new Decision Making (DM) scheme for MOD of conceptual missile shapes was presented, which is contrived to determine suitable tradeoffs from Pareto optimal set using interactive preference articulation. There are two objective functions, to maximize ratio of lift to drag and to minimize radar cross-section (RCS) value. 3D computational electromagnetic solver was used to evaluate RCS, electromagnetic performance. 3D Navier-Stokes flow solver was adopted to evaluate aerodynamic performance. A flight mechanics solver was used to analyze the stability of the missile. Based on the MOEA, a synergetic optimization of missile shapes for aerodynamic and radar cross-section performance is completed. The results show that the proposed approach can be used in more complex optimization case of flight vehicles.
Xu, Gang; Liang, Xifeng; Yao, Shuanbao; Chen, Dawei; Li, Zhiwei
2017-01-01
Minimizing the aerodynamic drag and the lift of the train coach remains a key issue for high-speed trains. With the development of computing technology and computational fluid dynamics (CFD) in the engineering field, CFD has been successfully applied to the design process of high-speed trains. However, developing a new streamlined shape for high-speed trains with excellent aerodynamic performance requires huge computational costs. Furthermore, relationships between multiple design variables and the aerodynamic loads are seldom obtained. In the present study, the Kriging surrogate model is used to perform a multi-objective optimization of the streamlined shape of high-speed trains, where the drag and the lift of the train coach are the optimization objectives. To improve the prediction accuracy of the Kriging model, the cross-validation method is used to construct the optimal Kriging model. The optimization results show that the two objectives are efficiently optimized, indicating that the optimization strategy used in the present study can greatly improve the optimization efficiency and meet the engineering requirements.
Stability-Constrained Aerodynamic Shape Optimization with Applications to Flying Wings
Mader, Charles Alexander
A set of techniques is developed that allows the incorporation of flight dynamics metrics as an additional discipline in a high-fidelity aerodynamic optimization. Specifically, techniques for including static stability constraints and handling qualities constraints in a high-fidelity aerodynamic optimization are demonstrated. These constraints are developed from stability derivative information calculated using high-fidelity computational fluid dynamics (CFD). Two techniques are explored for computing the stability derivatives from CFD. One technique uses an automatic differentiation adjoint technique (ADjoint) to efficiently and accurately compute a full set of static and dynamic stability derivatives from a single steady solution. The other technique uses a linear regression method to compute the stability derivatives from a quasi-unsteady time-spectral CFD solution, allowing for the computation of static, dynamic and transient stability derivatives. Based on the characteristics of the two methods, the time-spectral technique is selected for further development, incorporated into an optimization framework, and used to conduct stability-constrained aerodynamic optimization. This stability-constrained optimization framework is then used to conduct an optimization study of a flying wing configuration. This study shows that stability constraints have a significant impact on the optimal design of flying wings and that, while static stability constraints can often be satisfied by modifying the airfoil profiles of the wing, dynamic stability constraints can require a significant change in the planform of the aircraft in order for the constraints to be satisfied.
Gagnon, Hugo
This thesis represents a step forward to bring geometry parameterization and control on par with the disciplinary analyses involved in shape optimization, particularly high-fidelity aerodynamic shape optimization. Central to the proposed methodology is the non-uniform rational B-spline, used here to develop a new geometry generator and geometry control system applicable to the aerodynamic design of both conventional and unconventional aircraft. The geometry generator adopts a component-based approach, where any number of predefined but modifiable (parametric) wing, fuselage, junction, etc., components can be arbitrarily assembled to generate the outer mold line of aircraft geometry. A unique Python-based user interface incorporating an interactive OpenGL windowing system is proposed. Together, these tools allow for the generation of high-quality, C2 continuous (or higher), and customized aircraft geometry with fast turnaround. The geometry control system tightly integrates shape parameterization with volume mesh movement using a two-level free-form deformation approach. The framework is augmented with axial curves, which are shown to be flexible and efficient at parameterizing wing systems of arbitrary topology. A key aspect of this methodology is that very large shape deformations can be achieved with only a few, intuitive control parameters. Shape deformation consumes a few tenths of a second on a single processor and surface sensitivities are machine accurate. The geometry control system is implemented within an existing aerodynamic optimizer comprising a flow solver for the Euler equations and a sequential quadratic programming optimizer. Gradients are evaluated exactly with discrete-adjoint variables. The algorithm is first validated by recovering an elliptical lift distribution on a rectangular wing, and then demonstrated through the exploratory shape optimization of a three-pronged feathered winglet leading to a span efficiency of 1.22 under a height
Leading Edge Device Aerodynamic Optimization
Directory of Open Access Journals (Sweden)
Marius Gabriel COJOCARU
2015-12-01
Full Text Available Leading edge devices are conventionally used as aerodynamic devices that enhance performances during landing and in some cases during takeoff. The need to increase the efficiency of the aircrafts has brought the idea of maintaining as much as possible a laminar flow over the wings. This is possible only when the leading edge of the wings is free from contamination, therefore using the leading edge devices with the additional role of shielding during takeoff. Such a device based on the Krueger flap design is aerodynamically analyzed and optimized. The optimization comprises three steps: first, the positioning of the flap such that the shielding criterion is kept, second, the analysis of the flap size and third, the optimization of the flap shape. The first step is subject of a gradient based optimization process of the position described by two parameters, the position along the line and the deflection angle. For the third step the Adjoint method is used to gain insight on the shape of the Krueger flap that will extend the most the stall limit. All these steps have been numerically performed using Ansys Fluent and the results are presented for the optimized shape in comparison with the baseline configuration.
Aerodynamic Shape Optimization of Complex Aircraft Configurations via an Adjoint Formulation
Reuther, James; Jameson, Antony; Farmer, James; Martinelli, Luigi; Saunders, David
1996-01-01
This work describes the implementation of optimization techniques based on control theory for complex aircraft configurations. Here control theory is employed to derive the adjoint differential equations, the solution of which allows for a drastic reduction in computational costs over previous design methods (13, 12, 43, 38). In our earlier studies (19, 20, 22, 23, 39, 25, 40, 41, 42) it was shown that this method could be used to devise effective optimization procedures for airfoils, wings and wing-bodies subject to either analytic or arbitrary meshes. Design formulations for both potential flows and flows governed by the Euler equations have been demonstrated, showing that such methods can be devised for various governing equations (39, 25). In our most recent works (40, 42) the method was extended to treat wing-body configurations with a large number of mesh points, verifying that significant computational savings can be gained for practical design problems. In this paper the method is extended for the Euler equations to treat complete aircraft configurations via a new multiblock implementation. New elements include a multiblock-multigrid flow solver, a multiblock-multigrid adjoint solver, and a multiblock mesh perturbation scheme. Two design examples are presented in which the new method is used for the wing redesign of a transonic business jet.
Perching aerodynamics and trajectory optimization
Wickenheiser, Adam; Garcia, Ephrahim
2007-04-01
Advances in smart materials, actuators, and control architecture have enabled new flight capabilities for aircraft. Perching is one such capability, described as a vertical landing maneuver using in-flight shape reconfiguration in lieu of high thrust generation. A morphing, perching aircraft design is presented that is capable of post stall flight and very slow landing on a vertical platform. A comprehensive model of the aircraft's aerodynamics, with special regard to nonlinear affects such as flow separation and dynamic stall, is discussed. Trajectory optimization using nonlinear programming techniques is employed to show the effects that morphing and nonlinear aerodynamics have on the maneuver. These effects are shown to decrease the initial height and distance required to initiate the maneuver, reduce the bounds on the trajectory, and decrease the required thrust for the maneuver. Perching trajectories comparing morphing versus fixed-configuration and stalled versus un-stalled aircraft are presented. It is demonstrated that a vertical landing is possible in the absence of high thrust if post-stall flight capabilities and vehicle reconfiguration are utilized.
National Aeronautics and Space Administration — In practically all air-vehicle MDO studies to date involving configuration shape optimization, dynamic Aeroservoelastic constraints had to be left out. Flutter, gust...
Continuous Aerodynamic Modelling of Entry Shapes
Dirkx, D.; Mooij, E.
2011-01-01
During the conceptual design phase of a re-entry vehicle, the vehicle shape can be varied and its impact on performance evaluated. To this end, the continuous modeling of the aerodynamic characteristics as a function of the shape is useful in exploring the full design space. Local inclination method
National Aeronautics and Space Administration — CFD-based design-oriented (DO) steady/unsteady aerodynamic analysis tools for Aeroelastic / Aeroservoelastic (AE/ASE) evaluation lag significantly behind other...
乘波体飞行器气动布局优化设计%Aerodynamic Shape Optimization of a Wave-Rider Vehicle
Institute of Scientific and Technical Information of China (English)
王允良
2013-01-01
The best aerodynamic shape for hypersonic cruis vehicle is the waverider which has a high lift-to-drag ratio. The accurate solutions of the flow field with conical shock wave were evaluated by Taylor-Maccoll equation, and then the parametric geometry of the wave-rider vehicle was generated with the reverse design method by tracking the streamlines of the flow field. With the flow solutions behind the conical shock wave, the reference temperature method was applied to compute the aerodynamic force coefficients of the wave-rider vehicle. The geometric parameters of the wave-rider vehicle were optimized with respect to the lift-to-drag ra⁃tio. In order to enhance the computation efficiency and the local searching ability of the optimization procedure, the improved Particle Swarm Optimization (PSO) algorithm was employed to obtain the optimal aerodynamic con⁃figuration of the waverider vehicle with the maximized lift-to-drag ratio.% 由于具有高升阻比,乘波体是高超声速巡航飞行器气动布局的首选方案。文章在求解圆锥激波流场精确解的基础上,应用流线追踪方法,建立了乘波体飞行器气动布局的参数化模型。在此基础上,对飞行器的气动力特性进行了估算。最后,以气动布局参数为设计变量,升阻比最大化为设计目标,对乘波体飞行器进行气动布局优化设计,应用改进的粒子群优化算法(Particle Swarm Optimization,PSO),对优化模型进行求解,得到了优化的气动布局设计方案。
Aerodynamic Shape Optimization for Wing Based on Non-uniform Rational B-spline%基于NURBS方法的机翼气动外形优化
Institute of Scientific and Technical Information of China (English)
马晓永; 范召林; 吴文华; 杨党国
2011-01-01
飞行器气动外形优化就是将设计对象的空气动力学性能分析与最优化方法相结合,通过不断改变设计对象的外形,使其气动性能在满足一定约束条件下达到最优.气动外形优化是一个涉及几何参数化、动网格、流场计算和寻优算法的综合应用平台.随着计算流体力学(CFD)的发展以及高性能计算机的使用,气动外形优化在现代飞行器设计中的作用愈加重要.为此建立了基于非均匀有理B样条(NURBS)参数化方法的机翼气动外形优化平台.优化过程中采用弹性网格变形法,由雷诺平均Navier-Stokes方程组和Baldwin-Lomax代数湍流模型求解流场,并用离散伴随方法进行目标函数梯度求解,最后结合序列二次规划( SQP)方法进行优化迭代.通过对ONERA M6机翼在跨声速条件下进行优化分析,结果表明在保持升力系数和机翼容积不变,马赫数Ma =0.84、迎角α=3.06°时,优化后机翼表面压力系数有明显变化,上翼面λ激波明显减弱,相对于原始外形优化后机翼阻力系数减小0.002 5,降幅达13.1％；优化实例验证了该方法有效可行.%Aerodynamic design optimization is to find the optimum of aircraft aerodynamic performance under certain constraints by changing the shape of the designed object. It facilitates the design process by automating both the performance a-nalysis and the optimization method. Aerodynamic design optimization is an integrated application of geometry parameterization, grid update, flow field solver and optimization method, and it has contributed to the design of aircraft with the maturity of computational fluid dynamics (CFD) and the progress of computer performance. This paper presents an aerodynamic wing shape optimization method based on non-uniform rational B-spline (NURBS), in which the mesh deformation is used with a spring-based smoothing method. The Reynolds-averaged Navier-Stokes equations with an algebraic turbulence model of
Structural shape optimization in multidisciplinary system synthesis
Sobieszczanski-Sobieski, Jaroslaw
1988-01-01
Structural shape optimization couples with other discipline optimization in the design of complex engineering systems. For instance, the wing structural weight and elastic deformations couple to aerodynamic loads and aircraft performance through drag. This coupling makes structural shape optimization a subtask in the overall vehicle synthesis. Decomposition methods for optimization and sensitivity analysis allow the specialized disciplinary methods to be used while the disciplines are temporarily decoupled, after which the interdisciplinary couplings are restored at the system level. Application of decomposition methods to structures-aerodynamics coupling in aircraft is outlined and illustrated with a numerical example of a transport aircraft. It is concluded that these methods may integrate structural and aerodynamic shape optimizations with the unified objective of the maximum aircraft performance.
Institute of Scientific and Technical Information of China (English)
吴文华; 范召林; 陈德华; 覃宁; 孟德虹
2012-01-01
After decades of studies, the potentialities of traditional wing-body configuration are almost exhausted. So, it is difficult to improve the performance of the traditional aerodynamic shape of transonic civil aircraft by conventional design method. In this paper we develop ADJOINT method based on aerodynamics optimization software-ADJOPT, and the software is used to optimize the wing of a transonic civil aircraft with fuselage and nacelle, which is already optimized by traditional way. The optimization is multi-parameter, high precise and taking the influence of the fuselage and nacelle into account. The software performs well and gets obvious performance improvement. The research shows that multi-parameter optimization has the ability to exploit potentialities of a high-performance shape and increases the aerodynamic performance of it.%发展了基于伴随算子的气动布局优化设计软件-ADJOPT,并将该软件用于经过传统设计方法优化的大飞机布局上,开展全机状态下的机翼多参数、高精度优化设计,计入了短舱和机身对机翼气动特性的影响,取得了明显的优化效果.研究结果表明,多参数优化设计能够充分挖掘一个优良布局的设计潜力,进一步提高布局性能.
Nash equilibrium and multi criterion aerodynamic optimization
Tang, Zhili; Zhang, Lianhe
2016-06-01
Game theory and its particular Nash Equilibrium (NE) are gaining importance in solving Multi Criterion Optimization (MCO) in engineering problems over the past decade. The solution of a MCO problem can be viewed as a NE under the concept of competitive games. This paper surveyed/proposed four efficient algorithms for calculating a NE of a MCO problem. Existence and equivalence of the solution are analyzed and proved in the paper based on fixed point theorem. Specific virtual symmetric Nash game is also presented to set up an optimization strategy for single objective optimization problems. Two numerical examples are presented to verify proposed algorithms. One is mathematical functions' optimization to illustrate detailed numerical procedures of algorithms, the other is aerodynamic drag reduction of civil transport wing fuselage configuration by using virtual game. The successful application validates efficiency of algorithms in solving complex aerodynamic optimization problem.
Institute of Scientific and Technical Information of China (English)
肖友刚; 张平
2013-01-01
将大涡模拟法与Lighthill-Curle声学比拟理论相结合,计算了高速列车纵向对称面的气动噪声,探明了纵向对称面气动噪声的频谱特性及其变化规律,得出了车辆连接处的优化外形.结果表明,低频时,气动噪声幅值较大,随着频率升高,幅值下降.当列车运行速度一定时,距离气动噪声源越远,声压的衰减幅度越少.随着列车运行速度增加,距离气动噪声源越远,声压的增幅越小.脉动压力是气动噪声的源,在车辆连接处采用平滑的Nurbs曲线过渡,以减少列车运行过程中产生的脉动压力,能有效降低气动噪声.%The aerodynamic noise spectra of longitudinal symmetric plane of high-speed train were calculated and clarified by large eddy simulation and Lighthill-Curle acoustic theory. The optimal aerodynamic shape at vehicle junctions was got. The results show that the noise level of the aerodynamic noises is reduced greatly with the increase of frequency. When the train velocity is unchanged, the farther away from the aerodynamic noise sources, the less the attenuation rate of total noise level. With increase of the train velocity, the farther away from noise sources, the less the noise level increase. The fluctuation pressure is the source of aerodynamic noise, which can be reduced by using nurbs curve at vehicle junctions.
Wing Warping, Roll Control and Aerodynamic Optimization of Inflatable Wings
Simpson, Andrew
2005-11-01
The research presents work on aerodynamic control by warping inflatable wings. Inflatable wings are deformable by their nature. Mechanical manipulation of the wing's shape has been demonstrated to alter the performance and control the vehicle in flight by deforming the trailing edge of the wing near the wing tip. Predicting and correlating the forces required in deforming the wings to a particular shape and the deformation generated for a given internal pressure were conducted through the use of photogrammetry. This research focuses on optimizing the roll moments and aerodynamic performance of the vehicle, given the current level of wing warping ability. Predictions from lifting line theory applied to wing shape changes are presented. Comparisons from the experimental results are made with lifting line analysis for wings with arbitrary twist and the solutions are used to determine rolling moment and optimum L/D. Results from flight tests will also be presented.
CFD research, parallel computation and aerodynamic optimization
Ryan, James S.
1995-01-01
Over five years of research in Computational Fluid Dynamics and its applications are covered in this report. Using CFD as an established tool, aerodynamic optimization on parallel architectures is explored. The objective of this work is to provide better tools to vehicle designers. Submarine design requires accurate force and moment calculations in flow with thick boundary layers and large separated vortices. Low noise production is critical, so flow into the propulsor region must be predicted accurately. The High Speed Civil Transport (HSCT) has been the subject of recent work. This vehicle is to be a passenger vehicle with the capability of cutting overseas flight times by more than half. A successful design must surpass the performance of comparable planes. Fuel economy, other operational costs, environmental impact, and range must all be improved substantially. For all these reasons, improved design tools are required, and these tools must eventually integrate optimization, external aerodynamics, propulsion, structures, heat transfer and other disciplines.
Integrated structural-aerodynamic design optimization
Haftka, R. T.; Kao, P. J.; Grossman, B.; Polen, D.; Sobieszczanski-Sobieski, J.
1988-01-01
This paper focuses on the processes of simultaneous aerodynamic and structural wing design as a prototype for design integration, with emphasis on the major difficulty associated with multidisciplinary design optimization processes, their enormous computational costs. Methods are presented for reducing this computational burden through the development of efficient methods for cross-sensitivity calculations and the implementation of approximate optimization procedures. Utilizing a modular sensitivity analysis approach, it is shown that the sensitivities can be computed without the expensive calculation of the derivatives of the aerodynamic influence coefficient matrix, and the derivatives of the structural flexibility matrix. The same process is used to efficiently evaluate the sensitivities of the wing divergence constraint, which should be particularly useful, not only in problems of complete integrated aircraft design, but also in aeroelastic tailoring applications.
Parametric Deformation of Discrete Geometry for Aerodynamic Shape Design
Anderson, George R.; Aftosmis, Michael J.; Nemec, Marian
2012-01-01
We present a versatile discrete geometry manipulation platform for aerospace vehicle shape optimization. The platform is based on the geometry kernel of an open-source modeling tool called Blender and offers access to four parametric deformation techniques: lattice, cage-based, skeletal, and direct manipulation. Custom deformation methods are implemented as plugins, and the kernel is controlled through a scripting interface. Surface sensitivities are provided to support gradient-based optimization. The platform architecture allows the use of geometry pipelines, where multiple modelers are used in sequence, enabling manipulation difficult or impossible to achieve with a constructive modeler or deformer alone. We implement an intuitive custom deformation method in which a set of surface points serve as the design variables and user-specified constraints are intrinsically satisfied. We test our geometry platform on several design examples using an aerodynamic design framework based on Cartesian grids. We examine inverse airfoil design and shape matching and perform lift-constrained drag minimization on an airfoil with thickness constraints. A transport wing-fuselage integration problem demonstrates the approach in 3D. In a final example, our platform is pipelined with a constructive modeler to parabolically sweep a wingtip while applying a 1-G loading deformation across the wingspan. This work is an important first step towards the larger goal of leveraging the investment of the graphics industry to improve the state-of-the-art in aerospace geometry tools.
Shape Optimization of Wind Turbine Blades
DEFF Research Database (Denmark)
Wang, Xudong; Shen, Wen Zhong; Zhu, Wei Jun
2009-01-01
This paper presents a design tool for optimizing wind turbine blades. The design model is based on an aerodynamic/aero-elastic code that includes the structural dynamics of the blades and the Blade Element Momentum (BEM) theory. To model the main aero-elastic behaviour of a real wind turbine...... of the rotor. The design variables used in the current study are the blade shape parameters, including chord, twist and relative thickness. To validate the implementation of the aerodynamic/aero-elastic model, the computed aerodynamic results are compared to experimental data for the experimental rotor used...... in the European Commision-sponsored project Model Experiments in Controlled Conditions, (MEXICO) and the computed aero-elastic results are examined against the FLEX code for flow post the Tjereborg 2 MW rotor. To illustrate the optimization technique, three wind turbine rotors of different sizes (the MEXICO 25 k...
Proper Orthogonal Decomposition as Surrogate Model for Aerodynamic Optimization
Directory of Open Access Journals (Sweden)
Valentina Dolci
2016-01-01
Full Text Available A surrogate model based on the proper orthogonal decomposition is developed in order to enable fast and reliable evaluations of aerodynamic fields. The proposed method is applied to subsonic turbulent flows and the proper orthogonal decomposition is based on an ensemble of high-fidelity computations. For the construction of the ensemble, fractional and full factorial planes together with central composite design-of-experiment strategies are applied. For the continuous representation of the projection coefficients in the parameter space, response surface methods are employed. Three case studies are presented. In the first case, the boundary shape of the problem is deformed and the flow past a backward facing step with variable step slope is studied. In the second case, a two-dimensional flow past a NACA 0012 airfoil is considered and the surrogate model is constructed in the (Mach, angle of attack parameter space. In the last case, the aerodynamic optimization of an automotive shape is considered. The results demonstrate how a reduced-order model based on the proper orthogonal decomposition applied to a small number of high-fidelity solutions can be used to generate aerodynamic data with good accuracy at a low cost.
Aerodynamic assessment of humpback whale ventral fin shapes
2011-01-01
The ventral fins of the humpback whale (Megaptera novaeangliae) include a bulbous leading edge acting as a natural high-lift device. It has been suggested that application of this concept to wing design may yield advantages over traditional shapes (Miklosovic, et al., 2004). During the course of this project, the aerodynamic performance of whale fin models will be compared with conventional wing shapes. Based on the results of the study new wing design paradigms will be developed to improve t...
Longitudinal type-line optimization of high-speed train for low aerodynamic noise
Institute of Scientific and Technical Information of China (English)
肖友刚; 杨群; 孙亮; 时彧
2014-01-01
The basic head shape of high-speed train is determined by its longitudinal type-line (LTL), so it is crucial to optimize its aerodynamic performance. Based on the parametric modeling of LTL constructed by non-uniform relational B-spline (NURBS) and the fluctuation pressure obtained by large eddy simulation (LES), the Kriging surrogate model (KSM) of LTL was constructed for low aerodynamic noise, and the accuracy of the KSM was improved gradually by adding the sample point with maximum expected improvement (EI) and the optimal point from optimization. The optimal objective was searched with genetic algorithm (GA). The results show that the total fluctuation pressure level (FPL) of the optimal LTL can be 8.7 dB less than that of original one, and the shape optimization method is feasible for low aerodynamic noise design.
Duality based contact shape optimization
DEFF Research Database (Denmark)
Vondrák, Vít; Dostal, Zdenek; Rasmussen, John
2001-01-01
An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization.......An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization....
Aerodynamic Optimization of an Over-the-Wing-Nacelle-Mount Configuration
Directory of Open Access Journals (Sweden)
Daisuke Sasaki
2011-01-01
Full Text Available An over-the-wing-nacelle-mount airplane configuration is known to prevent the noise propagation from jet engines toward ground. However, the configuration is assumed to have low aerodynamic efficiency due to the aerodynamic interference effect between a wing and a nacelle. In this paper, aerodynamic design optimization is conducted to improve aerodynamic efficiency to be equivalent to conventional under-the-wing-nacelle-mount configuration. The nacelle and wing geometry are modified to achieve high lift-to-drag ratio, and the optimal geometry is compared with a conventional configuration. Pylon shape is also modified to reduce aerodynamic interference effect. The final wing-fuselage-nacelle model is compared with the DLR F6 model to discuss the potential of Over-the-Wing-Nacelle-Mount geometry for an environmental-friendly future aircraft.
Comparison of aerodynamic characteristics of pentagonal and hexagonal shaped bridge decks
Haque, Md. Naimul; Katsuchi, Hiroshi; Yamada, Hitoshi; Nishio, Mayuko
2016-07-01
Aerodynamics of the long-span bridge deck should be well understood for an efficient design of the bridge system. For practical bridges various deck shapes are being recommended and adopted, yet not all of their aerodynamic behaviors are well interpreted. In the present study, a numerical investigation was carried out to explore the aerodynamic characteristics of pentagonal and hexagonal shaped bridge decks. A relative comparison of steady state aerodynamic responses was made and the flow field was critically analyzed for better understanding the aerodynamic responses. It was found that the hexagonal shaped bridge deck has better aerodynamic characteristics as compared to the pentagonal shaped bridge deck.
Optimization of structural shapes
Durelli, A. J.
1981-04-01
The direct design of shapes of two dimensional structures, loaded in their plane, within specified design constraints and exhibiting optimum distribution of stresses is studied. Photoelasticity and a large field diffused polariscope is used. The optimization process involves the removal of material (with a hand file or router) from the low stress portions of the hole boundary of the model till an isochromatic fringe coincides with the boundary both on the tensile and compressive segments. Applications are also shown to the design of dove tails and slots in turbine blades and rotors, and to the design of star shaped solid propellant grains for rockets, both for the case of parallel side rays and enlarged tip of rays. The use of other methods, in particular the method using finite elements, to optimize structural forms is discussed.
Sensitivity Analysis and Optimization of Aerodynamic Configurations with Blend Surfaces
Thomas, A. M.; Tiwari, S. N.
1997-01-01
A novel (geometrical) parametrization procedure using solutions to a suitably chosen fourth order partial differential equation is used to define a class of airplane configurations. Inclusive in this definition are surface grids, volume grids, and grid sensitivity. The general airplane configuration has wing, fuselage, vertical tail and horizontal tail. The design variables are incorporated into the boundary conditions, and the solution is expressed as a Fourier series. The fuselage has circular cross section, and the radius is an algebraic function of four design parameters and an independent computational variable. Volume grids are obtained through an application of the Control Point Form method. A graphic interface software is developed which dynamically changes the surface of the airplane configuration with the change in input design variable. The software is made user friendly and is targeted towards the initial conceptual development of any aerodynamic configurations. Grid sensitivity with respect to surface design parameters and aerodynamic sensitivity coefficients based on potential flow is obtained using an Automatic Differentiation precompiler software tool ADIFOR. Aerodynamic shape optimization of the complete aircraft with twenty four design variables is performed. Unstructured and structured volume grids and Euler solutions are obtained with standard software to demonstrate the feasibility of the new surface definition.
Adjoint gradient-based approach for aerodynamic optimization of transport aircraft
Ilic, Caslav
2013-01-01
Aerodynamic design of transport aircraft has been steadily improved over past several decades, to the point where today highly-detailed shape control is needed to achieve further improvements. Aircraft manufacturers are therefore increasingly looking into formal optimization methods, driving high-fidelity CFD analysis of finely-parametrized candidate designs. We present an adjoint gradient-based approach for maximizing the aerodynamic performance index relevant to cruise-climb mission segment...
Aerodynamic modelling and optimization of axial fans
Energy Technology Data Exchange (ETDEWEB)
Noertoft Soerensen, Dan
1998-01-01
A numerically efficient mathematical model for the aerodynamics of low speed axial fans of the arbitrary vortex flow type has been developed. The model is based on a blade-element principle, whereby the rotor is divided into a number of annular stream tubes. For each of these stream tubes relations for velocity, pressure and radial position are derived from the conservation laws for mass, tangential momentum and energy. The equations are solved using the Newton-Raphson methods, and solutions converged to machine accuracy are found at small computing costs. The model has been validated against published measurements on various fan configurations, comprising two rotor-only fan stages, a counter-rotating fan unit and a stator-rotor stator stage. Comparisons of local and integrated properties show that the computed results agree well with the measurements. Optimizations have been performed to maximize the mean value of fan efficiency in a design interval of flow rates, thus designing a fan which operates well over a range of different flow conditions. The optimization scheme was used to investigate the dependence of maximum efficiency on 1: the number of blades, 2: the width of the design interval and 3: the hub radius. The degree of freedom in the choice of design variable and constraints, combined with the design interval concept, provides a valuable design-tool for axial fans. To further investigate the use of design optimization, a model for the vortex shedding noise from the trailing edge of the blades has been incorporated into the optimization scheme. The noise emission from the blades was minimized in a flow rate design point. Optimizations were performed to investigate the dependence of the noise on 1: the number of blades, 2: a constraint imposed on efficiency and 3: the hub radius. The investigations showed, that a significant reduction of noise could be achieved, at the expense of a small reduction in fan efficiency. (EG) 66 refs.
Wake shape and its effects on aerodynamic characteristics
Emdad, H.; Lan, C. E.
1986-01-01
The wake shape under symmetrical flight conditions and its effects on aerodynamic characteristics are examined. In addition, the effect of wake shape in sideslip and discrete vortices such as strake or forebody vortex on lateral characteristics is presented. The present numerical method for airplane configurations, which is based on discretization of the vortex sheet into vortex segments, verified the symmetrical and asymmetrical roll-up process of the trailing vortices. Also, the effect of wing wake on tail planes is calculated. It is concluded that at high lift the assumption of flat wake for longitudinal and lateral-directional characteristics should be reexamined.
Aerodynamic Optimization of Micro Aerial Vehicle
Directory of Open Access Journals (Sweden)
Siew Ping Yeong
2016-01-01
Full Text Available Computational fluid dynamics (CFD study was done on the propeller design of a micro aerial vehicle (quadrotor-typed to optimize its aerodynamic performance via Shear Stress Transport K-Omega (SST k-ω turbulence model. The quadrotor model used was WL-V303 Seeker. The design process started with airfoils selection and followed by the evaluation of drone model in hovering and cruising conditions. To sustain a 400g payload, by Momentum Theory an ideal thrust of 5.4 N should be generated by each rotor of the quadrotor and this resulted in an induced velocity of 7.4 m/s on the propeller during hovering phase, equivalent to Reynolds number of 10403 at 75% of the propeller blade radius. There were 6 propellers investigated at this Reynolds number. Sokolov airfoil which produced the largest lift-to-drag ratio was selected for full drone installation to be compared with the original model (benchmark. The CFD results showed that the Sokolov propeller generated 0.76 N of thrust more than the benchmark propeller at 7750 rpm. Despite generating higher thrust, higher drag was also experienced by the drone installed with Sokolov propellers. This resulted in lower lift-to-drag ratio than the benchmark propellers. It was also discovered that the aerodynamic performance of the drone could be further improved by changing the rotating direction of each rotor. Without making changes on the structural design, the drone performance increased by 39.58% in terms of lift-to-drag ratio by using this method.
A quantitative flow visualization technique for on-site sport aerodynamics optimization
Sciacchitano, A.; Caridi, G.; Scarano, F.
2015-01-01
Aerodynamics plays a crucial role in many speed sports, where races are often won by fractions of a second. A thorough understanding of the flow field around an athlete is of paramount importance to optimize the athletes’ posture, garment roughness and equipment shape to achieve the minimum aerodyna
Combined Shape and Topology Optimization
DEFF Research Database (Denmark)
Christiansen, Asger Nyman
Shape and topology optimization seeks to compute the optimal shape and topology of a structure such that one or more properties, for example stiffness, balance or volume, are improved. The goal of the thesis is to develop a method for shape and topology optimization which uses the Deformable...... Simplicial Complex (DSC) method. Consequently, we present a novel method which combines current shape and topology optimization methods. This method represents the surface of the structure explicitly and discretizes the structure into non-overlapping elements, i.e. a simplicial complex. An explicit surface...... representation usually limits the optimization to minor shape changes. However, the DSC method uses a single explicit representation and still allows for large shape and topology changes. It does so by constantly applying a set of mesh operations during deformations of the structure. Using an explicit instead...
Aerodynamic design optimization of nacelle/pylon position on an aircraft
Institute of Scientific and Technical Information of China (English)
Li Jing; Gao Zhenghong; Huang Jiangtao; Zhao Ke
2013-01-01
The arbitrary space-shape free form deformation (FFD) method developed in this paper is based on non-uniform rational B-splines (NURBS) basis function and used for the integral parameterization of nacelle-pylon geometry.The multi-block structured grid deformation technique is established by Delaunay graph mapping method.The optimization objects of aerodynamic characteristics are evaluated by solving Navier-Stokes equations on the basis of multi-block structured grid.The advanced particle swarm optimization (PSO) is utilized as search algorithm,which combines the Kriging model as surrogate model during optimization.The optimization system is used for optimizing the nacelle location of DLR-F6 wing-body-pylon-nacelle.The results indicate that the aerodynamic interference between the parts is significantly reduced.The optimization design system established in this paper has extensive applications and engineering value.
Institute of Scientific and Technical Information of China (English)
TANG ZhiLi; BAI Wen; DONG Jun
2008-01-01
This paper introduces the virtual and real game concepts to investigate multi-criterion optimization for optimum shape design in aerodynamics. The constrained acljoint meth-odology is used as the basic optimizer. Furthermore, the above is combined with the vir-tual and real game strategies to treat single-point/multi-point airfoil optimization. In a symmetric Nash Game, each optimizer attempts to optimize one's own target with ex-change of symmetric information with others. A Nash equilibrium is just the compromised solution among the multiple criteria. Several kinds of airfoil splitting and design cases are shown for the utility of virtual and real game strategies in aerodynamic design. Successful design results confirm the validity and efficiency of the present design method.
Institute of Scientific and Technical Information of China (English)
2008-01-01
This paper introduces the virtual and real game concepts to investigate multi-criterion optimization for optimum shape design in aerodynamics. The constrained adjoint meth- odology is used as the basic optimizer. Furthermore, the above is combined with the vir- tual and real game strategies to treat single-point/multi-point airfoil optimization. In a symmetric Nash Game, each optimizer attempts to optimize one’s own target with ex- change of symmetric information with others. A Nash equilibrium is just the compromised solution among the multiple criteria. Several kinds of airfoil splitting and design cases are shown for the utility of virtual and real game strategies in aerodynamic design. Successful design results confirm the validity and efficiency of the present design method.
Directory of Open Access Journals (Sweden)
José F. Herbert-Acero
2014-01-01
Full Text Available This work presents a novel framework for the aerodynamic design and optimization of blades for small horizontal axis wind turbines (WT. The framework is based on a state-of-the-art blade element momentum model, which is complemented with the XFOIL 6.96 software in order to provide an estimate of the sectional blade aerodynamics. The framework considers an innovative nested-hybrid solution procedure based on two metaheuristics, the virtual gene genetic algorithm and the simulated annealing algorithm, to provide a near-optimal solution to the problem. The objective of the study is to maximize the aerodynamic efficiency of small WT (SWT rotors for a wide range of operational conditions. The design variables are (1 the airfoil shape at the different blade span positions and the radial variation of the geometrical variables of (2 chord length, (3 twist angle, and (4 thickness along the blade span. A wind tunnel validation study of optimized rotors based on the NACA 4-digit airfoil series is presented. Based on the experimental data, improvements in terms of the aerodynamic efficiency, the cut-in wind speed, and the amount of material used during the manufacturing process were achieved. Recommendations for the aerodynamic design of SWT rotors are provided based on field experience.
The Effect of Aerodynamic Evaluators on the Multi-Objective Optimization of Flatback Airfoils
Miller, M.; Slew, K. Lee; Matida, E.
2016-09-01
With the long lengths of today's wind turbine rotor blades, there is a need to reduce the mass, thereby requiring stiffer airfoils, while maintaining the aerodynamic efficiency of the airfoils, particularly in the inboard region of the blade where structural demands are highest. Using a genetic algorithm, the multi-objective aero-structural optimization of 30% thick flatback airfoils was systematically performed for a variety of aerodynamic evaluators such as lift-to-drag ratio (Cl/Cd), torque (Ct), and torque-to-thrust ratio (Ct/Cn) to determine their influence on airfoil shape and performance. The airfoil optimized for Ct possessed a 4.8% thick trailing-edge, and a rather blunt leading-edge region which creates high levels of lift and correspondingly, drag. It's ability to maintain similar levels of lift and drag under forced transition conditions proved it's insensitivity to roughness. The airfoil optimized for Cl/Cd displayed relatively poor insensitivity to roughness due to the rather aft-located free transition points. The Ct/Cn optimized airfoil was found to have a very similar shape to that of the Cl/Cd airfoil, with a slightly more blunt leading-edge which aided in providing higher levels of lift and moderate insensitivity to roughness. The influence of the chosen aerodynamic evaluator under the specified conditions and constraints in the optimization of wind turbine airfoils is shown to have a direct impact on the airfoil shape and performance.
Aerodynamic Modelling and Optimization of Axial Fans
DEFF Research Database (Denmark)
Sørensen, Dan Nørtoft
A numerically efficient mathematical model for the aerodynamics oflow speed axial fans of the arbitrary vortex flow type has been developed.The model is based on a blade-element principle, whereby therotor is divided into a number of annular streamtubes.For each of these streamtubes relations...... for velocity, pressure andradial position are derived from the conservationlaws for mass, tangential momentum and energy.The resulting system of equations is non-linear and, dueto mass conservation and pressure equilibrium far downstream of the rotor,strongly coupled.The equations are solved using the Newton...
Aerodynamic Optimization of a Winglet Design
Directory of Open Access Journals (Sweden)
Yahiaoui T.
2013-04-01
Full Text Available In the present study, an experimental study is presented for a flow around an isolated wing equipped by a winglet and profiled with Naca 0012. Several cases of winglets were tested according to the angle ß: 0°, 55°, 65°and 75°. For all these cases at a velocity of 20, 30 and 40 meters per second, wind tunnel tests are performed and compared for different angles of incidence. It is observed that the aerodynamic performance of the winglet with β= 55° differ favorably for positive angle of incidence compared for other cases.
Improved Aerodynamic Analysis for Hybrid Wing Body Conceptual Design Optimization
Gern, Frank H.
2012-01-01
This paper provides an overview of ongoing efforts to develop, evaluate, and validate different tools for improved aerodynamic modeling and systems analysis of Hybrid Wing Body (HWB) aircraft configurations. Results are being presented for the evaluation of different aerodynamic tools including panel methods, enhanced panel methods with viscous drag prediction, and computational fluid dynamics. Emphasis is placed on proper prediction of aerodynamic loads for structural sizing as well as viscous drag prediction to develop drag polars for HWB conceptual design optimization. Data from transonic wind tunnel tests at the Arnold Engineering Development Center s 16-Foot Transonic Tunnel was used as a reference data set in order to evaluate the accuracy of the aerodynamic tools. Triangularized surface data and Vehicle Sketch Pad (VSP) models of an X-48B 2% scale wind tunnel model were used to generate input and model files for the different analysis tools. In support of ongoing HWB scaling studies within the NASA Environmentally Responsible Aviation (ERA) program, an improved finite element based structural analysis and weight estimation tool for HWB center bodies is currently under development. Aerodynamic results from these analyses are used to provide additional aerodynamic validation data.
Study on Aerodynamic Design Optimization of Turbomachinery Blades
Institute of Scientific and Technical Information of China (English)
Naixing CHEN; Hongwu ZHANG; Weiguang HUANG; Yanji XU
2005-01-01
This paper describes the study on aerodynamics design optimization of turbomachinery blading developed by the authors at the Institute of Engineering Thermophysics, Chinese Academy of Sciences, during the recent few years. The present paper describes the aspects mainly on how to use a rapid approach of profiling a 3D blading and of grid generation for computation, a fast and accurate viscous computation method and an appropriate optimization methodology_ including a blade parameterization algorithm to optimize turbomachinery blading aerodynamically. Any blade configuration can be expressed by three curves, they are the camber lines, the thickness distributions and the radial stacking line, and then the blade geometry can be easily parameterized by a number of parameters with three polynomials. A gradient-based parameterization analytical method and a response surface method were applied herein for blade optimization. It was found that the optimization process provides reliable design for turbomachinery with reasonable computing time.
AERODYNAMIC OPTIMIZATION DESIGN OF LOW ASPECT RATIO TRANSONIC TURBINE STAGE
Institute of Scientific and Technical Information of China (English)
SONG Liming; LI Jun; FENG Zhenping
2006-01-01
The advanced optimization method named as adaptive range differential evolution (ARDE)is developed. The optimization performance of ARDE is demonstrated using a typical mathematical test and compared with the standard genetic algorithm and differential evolution. Combined with parallel ARDE, surface modeling method and Navier-Stokes solution, a new automatic aerodynamic optimization method is presented. A low aspect ratio transonic turbine stage is optimized for the maximization of the isentropic efficiency with forty-one design variables in total. The coarse-grained parallel strategy is applied to accelerate the design process using 15 CPUs. The isentropic efficiency of the optimum design is 1.6% higher than that of the reference design. The aerodynamic performance of the optimal design is much better than that of the reference design.
Transonic Wing Shape Optimization Using a Genetic Algorithm
Holst, Terry L.; Pulliam, Thomas H.; Kwak, Dochan (Technical Monitor)
2002-01-01
A method for aerodynamic shape optimization based on a genetic algorithm approach is demonstrated. The algorithm is coupled with a transonic full potential flow solver and is used to optimize the flow about transonic wings including multi-objective solutions that lead to the generation of pareto fronts. The results indicate that the genetic algorithm is easy to implement, flexible in application and extremely reliable.
Microgenetic optimization algorithm for optimal wavefront shaping
Anderson, Benjamin R; Gunawidjaja, Ray; Eilers, Hergen
2015-01-01
One of the main limitations of utilizing optimal wavefront shaping in imaging and authentication applications is the slow speed of the optimization algorithms currently being used. To address this problem we develop a micro-genetic optimization algorithm ($\\mu$GA) for optimal wavefront shaping. We test the abilities of the $\\mu$GA and make comparisons to previous algorithms (iterative and simple-genetic) by using each algorithm to optimize transmission through an opaque medium. From our experiments we find that the $\\mu$GA is faster than both the iterative and simple-genetic algorithms and that both genetic algorithms are more resistant to noise and sample decoherence than the iterative algorithm.
Efficient optimization of integrated aerodynamic-structural design
Haftka, R. T.; Grossman, B.; Eppard, W. M.; Kao, P. J.; Polen, D. M.
1989-01-01
Techniques for reducing the computational complexity of multidisciplinary design optimization (DO) of aerodynamic structures are described and demonstrated. The basic principles of aerodynamic and structural DO are reviewed; the formulation of the combined DO problem is outlined; and particular attention is given to (1) the application of perturbation methods to cross-sensitivity computations and (2) numerical approximation procedures. Trial DOs of a simple sailplane design are presented in tables and graphs and discussed in detail. The IBM 3090 CPU time for the entire integrated DO was reduced from an estimated 10 h to about 6 min.
Shape of optimal active flagella
Eloy, Christophe
2013-01-01
Many eukaryotic cells use the active waving motion of flexible flagella to self-propel in viscous fluids. However, the criteria governing the selection of particular flagellar waveforms among all possible shapes has proved elusive so far. To address this question, we derive computationally the optimal shape of an internally-forced periodic planar flagellum deforming as a travelling wave. The optimum is here defined as the shape leading to a given swimming speed with minimum energetic cost. To calculate the energetic cost though, we consider the irreversible internal power expanded by the molecular motors forcing the flagellum, only a portion of which ending up dissipated in the fluid. This optimisation approach allows us to derive a family of shapes depending on a single dimensionless number quantifying the relative importance of elastic to viscous effects: the Sperm number. The computed optimal shapes are found to agree with the waveforms observed on spermatozoon of marine organisms, thus suggesting that the...
Topological Derivatives in Shape Optimization
Novotny, Antonio André
2013-01-01
The topological derivative is defined as the first term (correction) of the asymptotic expansion of a given shape functional with respect to a small parameter that measures the size of singular domain perturbations, such as holes, inclusions, defects, source-terms and cracks. Over the last decade, topological asymptotic analysis has become a broad, rich and fascinating research area from both theoretical and numerical standpoints. It has applications in many different fields such as shape and topology optimization, inverse problems, imaging processing and mechanical modeling including synthesis and/or optimal design of microstructures, sensitivity analysis in fracture mechanics and damage evolution modeling. Since there is no monograph on the subject at present, the authors provide here the first account of the theory which combines classical sensitivity analysis in shape optimization with asymptotic analysis by means of compound asymptotic expansions for elliptic boundary value problems. This book is intende...
Aerodynamic drag from two tubes in side-by-side arrangement for different tube shapes
Directory of Open Access Journals (Sweden)
Олександр Михайлович Терех
2016-06-01
Full Text Available Experimental investigations of aerodynamic drag from two tubes in side-by-side arrangement for different tube shapes in the range of Reynolds numbers from 4000 to16000 are performed. Comparison of experimental data is executed. It is set, that the tubes of drop-shaped form have less aerodynamic drag and the tubes of flat-oval and dumb-bell forms have greater drag as compared to drag of circular tubes
Mesh Optimization for Ground Vehicle Aerodynamics
Adrian Gaylard; Essam F Abo-Serie; Nor Elyana Ahmad
2010-01-01
Mesh optimization strategy for estimating accurate drag of a ground vehicle is proposed based on examining the effect of different mesh parameters. The optimized mesh parameters were selected using design of experiment (DOE) method to be able to work in a...
Improved aerodynamic design of turbomachinery bladings by numerical optimization
Energy Technology Data Exchange (ETDEWEB)
Burguburu, St.; Le Pape, A. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), Applied Aerodynamics Dept. 29, 92 - Chatillon (France)
2003-06-01
The aerodynamic optimization of a transonic compressor is reported in this paper. The Q3D Navier-Stokes solver COLIBRI is coupled to a gradient-based method (CONMIN) and to a genetic algorithm (GADO). The suction side of a 2-D blade is optimized by using both optimization methods with a significant efficiency improvement. In 3-D, the performance improvement is obtained by modifying the suction surface of a transonic compressor with a Bezier surface and by using the CANARI solver coupled to the gradient method (CONMIN). (authors)
Mesh Optimization for Ground Vehicle Aerodynamics
Directory of Open Access Journals (Sweden)
Adrian Gaylard
2010-04-01
Full Text Available
Mesh optimization strategy for estimating accurate drag of a ground vehicle is proposed based on examining the effect of different mesh parameters. The optimized mesh parameters were selected using design of experiment (DOE method to be able to work in a limited memory environment and in a reasonable amount of time but without compromising the accuracy of results. The study was further extended to take into account the car model size effect. Three car model sizes have been investigated and compared with MIRA scale wind tunnel results. Parameters that lead to drag value closer to experiment with less memory and computational time have been identified. Scaling the optimized mesh size with the length of car model was successfully used to predict the drag of the other car sizes with reasonable accuracy. This investigation was carried out using STARCCM+ commercial software package, however the findings can be applied to any other CFD package.
Computational fluid dynamics based aerodynamic optimization of the wind tunnel primary nozzle
Jan, Kolář; Václav, Dvořák
2012-06-01
The aerodynamic shape optimization of the supersonic flat nozzle is the aim of proposed paper. The nozzle discussed, is applied as a primary nozzle of the inlet part of supersonic wind tunnel. Supersonic nozzles of the measure area inlet parts need to guarantee several requirements of flow properties and quality. Mach number and minimal differences between real and required velocity and turbulence profiles at the nozzle exit are the most important parameters to meet. The aerodynamic shape optimization of the flat 2D nozzle in Computational Fluid Dynamics (CFD) is employed to reach as uniform exit velocity profile as possible, with the mean Mach number 1.4. Optimization process does not use any of standard routines of global or local optimum searching. Instead, newly formed routine, which exploits shape-based oriented sequence of nozzles, is used to research within whole discretized parametric space. The movement within optimization process is not driven by gradient or evolutionary too, instead, the Path of Minimal Shape Deformation is followed. Dynamic mesh approach is used to deform the shape and mesh from the actual nozzle to the subsequent one. Dynamic deformation of mesh allows to speed up whole converging process as an initialization of flow at the newly formed mesh is based on afore-computed shape. Shape-based similarity query in field of supersonic nozzles is discussed and applied. Evolutionary technique with genetic algorithm is used to search for minimal deformational path. As a result, the best variant from the set of solved shapes is analyzed at the base of momentum coefficient and desired Mach number at the nozzle exit.
Application of surrogate-based global optimization to aerodynamic design
Pérez, Esther
2016-01-01
Aerodynamic design, like many other engineering applications, is increasingly relying on computational power. The growing need for multi-disciplinarity and high fidelity in design optimization for industrial applications requires a huge number of repeated simulations in order to find an optimal design candidate. The main drawback is that each simulation can be computationally expensive – this becomes an even bigger issue when used within parametric studies, automated search or optimization loops, which typically may require thousands of analysis evaluations. The core issue of a design-optimization problem is the search process involved. However, when facing complex problems, the high-dimensionality of the design space and the high-multi-modality of the target functions cannot be tackled with standard techniques. In recent years, global optimization using meta-models has been widely applied to design exploration in order to rapidly investigate the design space and find sub-optimal solutions. Indeed, surrogat...
Optimal plane change by low aerodynamic forces
Vinh, Nguyen X.; Ma, Der-Ming
1990-01-01
This paper presents the exact dimensionless equations of motion and the necessary conditions for the computation of the optimal trajectories of a hypervelocity vehicle flying through a nonrotating spherical planetary atmosphere. It is shown that there are two types of maneuvers with nearly identical plane change. In the hard maneuver, the vehicle is pulled down to low altitude for aerodyamic plane change before exit at the prescribed final speed. In the slow maneuver which is described in detail in this paper, the vehicle remains in orbital flight with a small incremental plane change during each passage through the perigee. This maneuver requires several revolutions, and the technique for computation is similar to that in the problem of contraction of orbit.
Optimal shapes for self-propelled swimmers
Koumoutsakos, Petros; van Rees, Wim; Gazzola, Mattia
2011-11-01
We optimize swimming shapes of three-dimensional self-propelled swimmers by combining the CMA- Evolution Strategy with a remeshed vortex method. We analyze the robustness of optimal shapes and discuss the near wake vortex dynamics for optimal speed and efficiency at Re=550. We also report preliminary results of optimal shapes and arrangements for multiple coordinated swimmers.
Flutter Derivatives Identification and Aerodynamic Performance of an Optimized Multibox Bridge Deck
Directory of Open Access Journals (Sweden)
Zhida Wang
2016-01-01
Full Text Available The bridge deck sections used for long-span suspension bridges have evolved through the years, from the compact box deck girders geometrical configurations to twin-box and three-box bridge decks sections. The latest generation of split and multiple-box bridge decks proved to have better aerodynamic behavior; thus further optimization methods are sought for such geometrical configurations. A new type of multibox bridge deck, consisting of four aerodynamically shaped deck boxes, two side decks for the traffic lanes and two middle decks for the railway traffic, connected between them by stabilizing beams, was tested in the wind tunnel for identifying the flutter derivatives and to verify the aerodynamic performance of the proposed multibox deck. Aerodynamic static force coefficients were measured for the multibox bridge deck model, scaled 1 : 80, for Reynolds numbers up to 5.1 × 105, under angles of attack between −8° and 8°. Iterative Least Squares (ILS method was employed for identifying the flutter derivatives of the multibox bridge deck model, based on the results obtained from the free vibration tests and based on the frequency analysis the critical flutter wind speed for the corresponding prototype of the multibox bridge was estimated at 188 m/s.
Aerodynamic Optimization of an Over-the-Wing-Nacelle-Mount Configuration
Daisuke Sasaki; Kazuhiro Nakahashi
2011-01-01
An over-the-wing-nacelle-mount airplane configuration is known to prevent the noise propagation from jet engines toward ground. However, the configuration is assumed to have low aerodynamic efficiency due to the aerodynamic interference effect between a wing and a nacelle. In this paper, aerodynamic design optimization is conducted to improve aerodynamic efficiency to be equivalent to conventional under-the-wing-nacelle-mount configuration. The nacelle and wing geometry are modified to achiev...
New trends in shape optimization
Leugering, Günter
2015-01-01
This volume reflects “New Trends in Shape Optimization” and is based on a workshop of the same name organized at the Friedrich-Alexander University Erlangen-Nürnberg in September 2013. During the workshop senior mathematicians and young scientists alike presented their latest findings. The format of the meeting allowed fruitful discussions on challenging open problems, and triggered a number of new and spontaneous collaborations. As such, the idea was born to produce this book, each chapter of which was written by a workshop participant, often with a collaborator. The content of the individual chapters ranges from survey papers to original articles; some focus on the topics discussed at the Workshop, while others involve arguments outside its scope but which are no less relevant for the field today. As such, the book offers readers a balanced introduction to the emerging field of shape optimization.
Institute of Scientific and Technical Information of China (English)
Tang Zhili; Dong Jun
2009-01-01
complete and complete decisions of the leader and followers respectively. Several design examples illustrate the efficiency of the coupling algorithms for multi-criterion aerodynamic design optimization problems.
Global Design Optimization for Aerodynamics and Rocket Propulsion Components
Shyy, Wei; Papila, Nilay; Vaidyanathan, Rajkumar; Tucker, Kevin; Turner, James E. (Technical Monitor)
2000-01-01
Modern computational and experimental tools for aerodynamics and propulsion applications have matured to a stage where they can provide substantial insight into engineering processes involving fluid flows, and can be fruitfully utilized to help improve the design of practical devices. In particular, rapid and continuous development in aerospace engineering demands that new design concepts be regularly proposed to meet goals for increased performance, robustness and safety while concurrently decreasing cost. To date, the majority of the effort in design optimization of fluid dynamics has relied on gradient-based search algorithms. Global optimization methods can utilize the information collected from various sources and by different tools. These methods offer multi-criterion optimization, handle the existence of multiple design points and trade-offs via insight into the entire design space, can easily perform tasks in parallel, and are often effective in filtering the noise intrinsic to numerical and experimental data. However, a successful application of the global optimization method needs to address issues related to data requirements with an increase in the number of design variables, and methods for predicting the model performance. In this article, we review recent progress made in establishing suitable global optimization techniques employing neural network and polynomial-based response surface methodologies. Issues addressed include techniques for construction of the response surface, design of experiment techniques for supplying information in an economical manner, optimization procedures and multi-level techniques, and assessment of relative performance between polynomials and neural networks. Examples drawn from wing aerodynamics, turbulent diffuser flows, gas-gas injectors, and supersonic turbines are employed to help demonstrate the issues involved in an engineering design context. Both the usefulness of the existing knowledge to aid current design
Some flows in shape optimization
Cardaliaguet, Pierre; 10.1007/s00205-006-0002-z
2010-01-01
Geometric flows related to shape optimization problems of Bernoulli type are investigated. The evolution law is the sum of a curvature term and a nonlocal term of Hele-Shaw type. We introduce generalized set solutions, the definition of which is widely inspired by viscosity solutions. The main result is an inclusion preservation principle for generalized solutions. As a consequence, we obtain existence, uniqueness and stability of solutions. Asymptotic behavior for the flow is discussed: we prove that the solutions converge to a generalized Bernoulli exterior free boundary problem.
Aerodynamic effects of simulated ice shapes on two-dimensional airfoils and a swept finite tail
Alansatan, Sait
An experimental study was conducted to investigate the effect of simulated glaze ice shapes on the aerodynamic performance characteristics of two-dimensional airfoils and a swept finite tail. The two dimensional tests involved two NACA 0011 airfoils with chords of 24 and 12 inches. Glaze ice shapes computed with the LEWICE code that were representative of 22.5-min and 45-min ice accretions were simulated with spoilers, which were sized to approximate the horn heights of the LEWICE ice shapes. Lift, drag, pitching moment, and surface pressure coefficients were obtained for a range of test conditions. Test variables included Reynolds number, geometric scaling, control deflection and the key glaze ice features, which were horn height, horn angle, and horn location. For the three-dimensional tests, a 25%-scale business jet empennage (BJE) with a T-tail configuration was used to study the effect of ice shapes on the aerodynamic performance of a swept horizontal tail. Simulated glaze ice shapes included the LEWICE and spoiler ice shapes to represent 9-min and 22.5-min ice accretions. Additional test variables included Reynolds number and elevator deflection. Lift, drag, hinge moment coefficients as well as boundary layer velocity profiles were obtained. The experimental results showed substantial degradation in aerodynamic performance of the airfoils and the swept horizontal tail due to the simulated ice shapes. For the two-dimensional airfoils, the largest aerodynamic penalties were obtained when the 3-in spoiler-ice, which was representative of 45-min glaze ice accretions, was set normal to the chord. Scale and Reynolds effects were not significant for lift and drag. However, pitching moments and pressure distributions showed great sensitivity to Reynolds number and geometric scaling. For the threedimensional study with the swept finite tail, the 22.5-min ice shapes resulted in greater aerodynamic performance degradation than the 9-min ice shapes. The addition of 24
Variable Camber Continuous Aerodynamic Control Surfaces and Methods for Active Wing Shaping Control
Nguyen, Nhan T. (Inventor)
2016-01-01
An aerodynamic control apparatus for an air vehicle improves various aerodynamic performance metrics by employing multiple spanwise flap segments that jointly form a continuous or a piecewise continuous trailing edge to minimize drag induced by lift or vortices. At least one of the multiple spanwise flap segments includes a variable camber flap subsystem having multiple chordwise flap segments that may be independently actuated. Some embodiments also employ a continuous leading edge slat system that includes multiple spanwise slat segments, each of which has one or more chordwise slat segment. A method and an apparatus for implementing active control of a wing shape are also described and include the determination of desired lift distribution to determine the improved aerodynamic deflection of the wings. Flap deflections are determined and control signals are generated to actively control the wing shape to approximate the desired deflection.
AERODYNAMIC CHARACTERISTICS ABOUT MINING DUMP TRUCK AND THE IMPROVEMENT OF HEAD SHAPE
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The external flow field around a certain mining dump truck was simulated. The airflow structure and the aerodynamic drag were discussed, and the relationship between airflow characteristics and aerodynamic drag were obtained. In order to solve the problem of head shape of the truck, three scenarios including edge rounding, installing splitter planes and their combination were put forward to improve the head shape through numerical simulation and analysis. The model and method were selected to be three dimensional and time-independent. The Reynolds-averaged Navier-Stokes equations were solved using the finite volume method. The RNG k-ε model was chosen for the closure of the turbulent quantities. The results show that the third scenario is the best one, because of its aerodynamic characteristics being better than those of unimproved model.
DEFF Research Database (Denmark)
Døssing, Mads
of very large machines introduces new problems in the practical design, and optimization tools are necessary. These must combine the dynamic eects of both aerodynamics and structure in an integrated optimization environment. This is referred to as aeroelastic optimization. The Ris DTU optimization...... software HAWTOPT has been used in this project. The quasi-steady aerodynamic module have been improved with a corrected blade element momentum method. A structure module has also been developed which lays out the blade structural properties. This is done in a simplied way allowing fast conceptual design...... studies and with focus on the overall properties relevant for the aeroelastic properties. Aeroelastic simulations in the time domain were carried out using the aeroelastic code HAWC2. With these modules coupled to HAWTOPT, optimizations have been made. In parallel with the developments of the mentioned...
Estimation of morphing airfoil shapes and aerodynamic loads using artificial hair sensors
Butler, Nathan Scott
An active area of research in adaptive structures focuses on the use of continuous wing shape changing methods as a means of replacing conventional discrete control surfaces and increasing aerodynamic efficiency. Although many shape-changing methods have been used since the beginning of heavier-than-air flight, the concept of performing camber actuation on a fully-deformable airfoil has not been widely applied. A fundamental problem of applying this concept to real-world scenarios is the fact that camber actuation is a continuous, time-dependent process. Therefore, if camber actuation is to be used in a closed-loop feedback system, one must be able to determine the instantaneous airfoil shape, as well as the aerodynamic loads, in real time. One approach is to utilize a new type of artificial hair sensors (AHS) developed at the Air Force Research Laboratory (AFRL) to determine the flow conditions surrounding deformable airfoils. In this study, AHS measurement data will be simulated by using the flow solver XFoil, with the assumption that perfect data with no noise can be collected from the AHS measurements. Such measurements will then be used in an artificial neural network (ANN) based process to approximate the instantaneous airfoil camber shape, lift coefficient, and moment coefficient at a given angle of attack. Additionally, an aerodynamic formulation based on the finite-state inflow theory has been developed to calculate the aerodynamic loads on thin airfoils with arbitrary camber deformations. Various aerodynamic properties approximated from the AHS/ANN system will be compared with the results of the finite-state inflow aerodynamic formulation in order to validate the approximation approach.
A high-rate shape memory alloy actuator for aerodynamic load control on wind turbines
Lara-Quintanilla, A.; Hulskamp, A.W.; Bersee, H.E.N.
2013-01-01
This paper discusses the development of a high rate shape memory alloy (SMA) driven actuator. The concept of the actuator was developed to act as aerodynamic load control surface on wind turbines. It was designed as a plate or beam-like structure with prestrained SMA wires embedded off its neutral a
Aerostructural Shape and Topology Optimization of Aircraft Wings
James, Kai
A series of novel algorithms for performing aerostructural shape and topology optimization are introduced and applied to the design of aircraft wings. An isoparametric level set method is developed for performing topology optimization of wings and other non-rectangular structures that must be modeled using a non-uniform, body-fitted mesh. The shape sensitivities are mapped to computational space using the transformation defined by the Jacobian of the isoparametric finite elements. The mapped sensitivities are then passed to the Hamilton-Jacobi equation, which is solved on a uniform Cartesian grid. The method is derived for several objective functions including mass, compliance, and global von Mises stress. The results are compared with SIMP results for several two-dimensional benchmark problems. The method is also demonstrated on a three-dimensional wingbox structure subject to fixed loading. It is shown that the isoparametric level set method is competitive with the SIMP method in terms of the final objective value as well as computation time. In a separate problem, the SIMP formulation is used to optimize the structural topology of a wingbox as part of a larger MDO framework. Here, topology optimization is combined with aerodynamic shape optimization, using a monolithic MDO architecture that includes aerostructural coupling. The aerodynamic loads are modeled using a three-dimensional panel method, and the structural analysis makes use of linear, isoparametric, hexahedral elements. The aerodynamic shape is parameterized via a set of twist variables representing the jig twist angle at equally spaced locations along the span of the wing. The sensitivities are determined analytically using a coupled adjoint method. The wing is optimized for minimum drag subject to a compliance constraint taken from a 2 g maneuver condition. The results from the MDO algorithm are compared with those of a sequential optimization procedure in order to quantify the benefits of the MDO
Huang, Ximing
1994-01-01
A variable-complexity design strategy with combined aerodynamic and structural optimization procedures is presented for the high speed civil transport design (HSCT). Variable-complexity analysis methods are used to reduce the computational expense. A finite element-model based structural optimization procedure with flexible loads is implemented to evaluate the wing bending material weight. Static aeroelastic effects, evaluated through the comparison of rigid and flexible win...
Design optimization of shape memory alloy structures
Langelaar, M.
2006-01-01
This thesis explores the possibilities of design optimization techniques for designing shape memory alloy structures. Shape memory alloys are materials which, after deformation, can recover their initial shape when heated. This effect can be used for actuation. Emerging applications for shape memory
ANALYTICAL APPROACH TO AERODYNAMIC CHARACTERISTICS OF THE HELICOPTER ROTOR WITH ANHEDRAL TIP SHAPE
Institute of Scientific and Technical Information of China (English)
1998-01-01
A new analytical approach, based on a lifting surface model and a full-span free wake analysis using the curved vortex element on the circular arc, is established for evaluating the aerodynamic characteristics of the helicopter rotor with an anhedral blade-tip and is emphasized to be applicable to various blade-tip configurations, such as the tapered, swept, anhedral and combined shapes. Sample calculations on the rotor aerodynamic characteristics for different anhedral tips in both hover and forward flight are performed. The results on the induced velocity, blade section lift distribution, tip vortex path and rotor performance are presented so that the effect of the anhedral tip on the rotor aerodynamic characteristics is fully analyzed.
Kuhlman, J. M.
1979-01-01
The aerodynamic design of a wind-tunnel model of a wing representative of that of a subsonic jet transport aircraft, fitted with winglets, was performed using two recently developed optimal wing-design computer programs. Both potential flow codes use a vortex lattice representation of the near-field of the aerodynamic surfaces for determination of the required mean camber surfaces for minimum induced drag, and both codes use far-field induced drag minimization procedures to obtain the required spanloads. One code uses a discrete vortex wake model for this far-field drag computation, while the second uses a 2-D advanced panel wake model. Wing camber shapes for the two codes are very similar, but the resulting winglet camber shapes differ widely. Design techniques and considerations for these two wind-tunnel models are detailed, including a description of the necessary modifications of the design geometry to format it for use by a numerically controlled machine for the actual model construction.
Estimation of morphing airfoil shape and aerodynamic load using artificial hair sensors
Butler, Nathan S.; Su, Weihua; Thapa Magar, Kaman S.; Reich, Gregory W.
2016-04-01
An active area of research in adaptive structures focuses on the use of continuous wing shape changing methods as a means of replacing conventional discrete control surfaces and increasing aerodynamic efficiency. Although many shape-changing methods have been used since the beginning of heavier-than-air flight, the concept of performing camber actuation on a fully-deformable airfoil has not been widely applied. A fundamental problem of applying this concept to real-world scenarios is the fact that camber actuation is a continuous, time-dependent process. Therefore, if camber actuation is to be used in a closed-loop feedback system, one must be able to determine the instantaneous airfoil shape as well as the aerodynamic loads at all times. One approach is to utilize a new type of artificial hair sensors developed at the Air Force Research Laboratory to determine the flow conditions surrounding deformable airfoils. In this work, the hair sensor measurement data will be simulated by using the flow solver XFoil, with the assumption that perfect data with no noise can be collected from the hair sensor measurements. Such measurements will then be used in an artificial neural network based process to approximate the instantaneous airfoil camber shape, lift coefficient, and moment coefficient at a given angle of attack. Various aerodynamic and geometrical properties approximated from the artificial hair sensor and artificial neural network system will be compared with the results of XFoil in order to validate the approximation approach.
Aerodynamic optimization of an HSCT configuration using variable-complexity modeling
Hutchison, M. G.; Mason, W. H.; Grossman, B.; Haftka, R. T.
1993-01-01
An approach to aerodynamic configuration optimization is presented for the high-speed civil transport (HSCT). A method to parameterize the wing shape, fuselage shape and nacelle placement is described. Variable-complexity design strategies are used to combine conceptual and preliminary-level design approaches, both to preserve interdisciplinary design influences and to reduce computational expense. Conceptual-design-level (approximate) methods are used to estimate aircraft weight, supersonic wave drag and drag due to lift, and landing angle of attack. The drag due to lift, wave drag and landing angle of attack are also evaluated using more detailed, preliminary-design-level techniques. New, approximate methods for estimating supersonic wave drag and drag due to lift are described. The methodology is applied to the minimization of the gross weight of an HSCT that flies at Mach 2.4 with a range of 5500 n.mi. Results are presented for wing planform shape optimization and for combined wing and fuselage optimization with nacelle placement. Case studies include both all-metal wings and advanced composite wings.
Airfoil shape optimization using non-traditional optimization technique and its validation
Directory of Open Access Journals (Sweden)
R. Mukesh
2014-07-01
Full Text Available Computational fluid dynamics (CFD is one of the computer-based solution methods which is more widely employed in aerospace engineering. The computational power and time required to carry out the analysis increase as the fidelity of the analysis increases. Aerodynamic shape optimization has become a vital part of aircraft design in the recent years. Generally if we want to optimize an airfoil we have to describe the airfoil and for that, we need to have at least hundred points of x and y co-ordinates. It is really difficult to optimize airfoils with this large number of co-ordinates. Nowadays many different schemes of parameter sets are used to describe general airfoil such as B-spline, and PARSEC. The main goal of these parameterization schemes is to reduce the number of needed parameters as few as possible while controlling the important aerodynamic features effectively. Here the work has been done on the PARSEC geometry representation method. The objective of this work is to introduce the knowledge of describing general airfoil using twelve parameters by representing its shape as a polynomial function. And also we have introduced the concept of Genetic Algorithm to optimize the aerodynamic characteristics of a general airfoil for specific conditions. A MATLAB program has been developed to implement PARSEC, Panel Technique, and Genetic Algorithm. This program has been tested for a standard NACA 2411 airfoil and optimized to improve its coefficient of lift. Pressure distribution and co-efficient of lift for airfoil geometries have been calculated using the Panel method. The optimized airfoil has improved co-efficient of lift compared to the original one. The optimized airfoil is validated using wind tunnel data.
Poirier, Vincent
Mesh deformation schemes play an important role in numerical aerodynamic optimization. As the aerodynamic shape changes, the computational mesh must adapt to conform to the deformed geometry. In this work, an extension to an existing fast and robust Radial Basis Function (RBF) mesh movement scheme is presented. Using a reduced set of surface points to define the mesh deformation increases the efficiency of the RBF method; however, at the cost of introducing errors into the parameterization by not recovering the exact displacement of all surface points. A secondary mesh movement is implemented, within an adjoint-based optimization framework, to eliminate these errors. The proposed scheme is tested within a 3D Euler flow by reducing the pressure drag while maintaining lift of a wing-body configured Boeing-747 and an Onera-M6 wing. As well, an inverse pressure design is executed on the Onera-M6 wing and an inverse span loading case is presented for a wing-body configured DLR-F6 aircraft.
Aerodynamic optimization of 3D wing based on iSIGHT
Institute of Scientific and Technical Information of China (English)
YIN Bo; XU Dian; AN Yi-ran; CHEN Yao-song
2008-01-01
A method for combining the CFD software, Fluent, with the iSIGHT design platform is presented to optimize a three-dimensional wing to ameliorate its aerodynamics performance. In the optimization design, two kinds of genetic algorithms, the Neighborhood Cultivation Genetic Algorithm (NCGA) and the Non-dominated Sorting Genetic Algorithm (NSGAII), are employed and the Navier-Stoke (N-S) equations are adopted to derive the aerodynamics functions of the 3D wing. The aerodynamic performance of the optimized wing has been significantly improved, which shows that the approach can be extended and employed in other cases.
Numerical Study of Aerodynamic Characteristics of a Symmetric NACA Section with Simulated Ice Shapes
Tabatabaei, N.; Cervantes, M. J.; Trivedi, C.; Aidanpää, Jan-Olof
2016-09-01
To develop a numerical model of icing on wind turbine blades, a CFD simulation was conducted to investigate the effect of critical ice accretions on the aerodynamic characteristics of a 0.610 m chord NACA 0011 airfoil section. Aerodynamic performance coefficients and pressure profile were calculated and compared with the available measurements for a chord Reynolds number of 1.83x106. Ice shapes were simulated with flat plates (spoiler-ice) extending along the span of the wing. Lift, drag, and pressure coefficients were calculated in zero angle of attack through the steady state and transient simulations. Different approaches of numerical studies have been applied to investigate the icing conditions on the blades. The simulated separated flow over the sharp spoilers is challenging and can be seen as a worst test case for validation. It allows determining a reliable strategy to simulate real ice shapes [1] for which the detailed validation cannot easily be provided.
Isogeometric Shape Optimization of Vibrating Membranes
DEFF Research Database (Denmark)
Nguyen, Dang Manh; Evgrafov, Anton; Gersborg, Allan Roulund;
2011-01-01
We consider a model problem of isogeometric shape optimization of vibrating membranes whose shapes are allowed to vary freely. The main obstacle we face is the need for robust and inexpensive extension of a B-spline parametrization from the boundary of a domain onto its interior, a task which has...... to be performed in every optimization iteration. We experiment with two numerical methods (one is based on the idea of constructing a quasi-conformal mapping, whereas the other is based on a spring-based mesh model) for carrying out this task, which turn out to work sufficiently well in the present situation. We...... perform a number of numerical experiments with our isogeometric shape optimization algorithm and present smooth, optimized membrane shapes. Our conclusion is that isogeometric analysis fits well with shape optimization....
Isogeometric analysis and shape optimization in electromagnetism
DEFF Research Database (Denmark)
Nguyen, Dang Manh
In this thesis a recently proposed numerical method for solving partial differential equations, isogeometric analysis (IGA), is utilized for the purpose of shape optimization, with a particular emphasis on applications to two-dimensional design problems arising in electromagnetic applications...... parametrization are combined into an iterative algorithm for shape optimization of two dimensional electromagnetic problems. The algorithm may also be relevant for problems in other engineering disciplines. Using the methods developed in this thesis, remarkably we have obtained antennas that perform one million...... times better than an earlier topology optimization result. This shows a great potential of shape optimization using IGA in the area of electromagnetic antenna design in particular, and for electromagnetic...
Generation of Fullspan Leading-Edge 3D Ice Shapes for Swept-Wing Aerodynamic Testing
Camello, Stephanie C.; Lee, Sam; Lum, Christopher; Bragg, Michael B.
2016-01-01
The deleterious effect of ice accretion on aircraft is often assessed through dry-air flight and wind tunnel testing with artificial ice shapes. This paper describes a method to create fullspan swept-wing artificial ice shapes from partial span ice segments acquired in the NASA Glenn Icing Reserch Tunnel for aerodynamic wind-tunnel testing. Full-scale ice accretion segments were laser scanned from the Inboard, Midspan, and Outboard wing station models of the 65% scale Common Research Model (CRM65) aircraft configuration. These were interpolated and extrapolated using a weighted averaging method to generate fullspan ice shapes from the root to the tip of the CRM65 wing. The results showed that this interpolation method was able to preserve many of the highly three dimensional features typically found on swept-wing ice accretions. The interpolated fullspan ice shapes were then scaled to fit the leading edge of a 8.9% scale version of the CRM65 wing for aerodynamic wind-tunnel testing. Reduced fidelity versions of the fullspan ice shapes were also created where most of the local three-dimensional features were removed. The fullspan artificial ice shapes and the reduced fidelity versions were manufactured using stereolithography.
Energy Technology Data Exchange (ETDEWEB)
Doessing, M.
2011-05-15
During the last decades the annual energy produced by wind turbines has increased dramatically and wind turbines are now available in the 5MW range. Turbines in this range are constantly being developed and it is also being investigated whether turbines as large as 10-20MW are feasible. The design of very large machines introduces new problems in the practical design, and optimization tools are necessary. These must combine the dynamic effects of both aerodynamics and structure in an integrated optimization environment. This is referred to as aeroelastic optimization. The Risoe DTU optimization software HAWTOPT has been used in this project. The quasi-steady aerodynamic module have been improved with a corrected blade element momentum method. A structure module has also been developed which lays out the blade structural properties. This is done in a simplified way allowing fast conceptual design studies and with focus on the overall properties relevant for the aeroelastic properties. Aeroelastic simulations in the time domain were carried out using the aeroelastic code HAWC2. With these modules coupled to HAWTOPT, optimizations have been made. In parallel with the developments of the mentioned numerical modules, focus has been on analysis and a fundamental understanding of the key parameters in wind turbine design. This has resulted in insight and an effective design methodology is presented. Using the optimization environment a 5MW wind turbine rotor has been optimized for reduced fatigue loads due to apwise bending moments. Among other things this has indicated that airfoils for wind turbine blades should have a high lift coefficient. The design methodology proved to be stable and a help in the otherwise challenging task of numerical aeroelastic optimization. (Author)
Isogeometric shape optimization in fluid mechanics
DEFF Research Database (Denmark)
Nørtoft, Peter; Gravesen, Jens
2013-01-01
The subject of this work is numerical shape optimization in fluid mechanics, based on isogeometric analysis. The generic goal is to design the shape of a 2-dimensional flow domain to minimize some prescribed objective while satisfying given geometric constraints. As part of the design problem...
Isogeometric shape optimization in fluid mechanics
DEFF Research Database (Denmark)
Nørtoft, Peter; Gravesen, Jens
2013-01-01
, the steady-state, incompressible Navier-Stokes equations, governing a laminar flow in the domain, must be solved. Based on isogeometric analysis, we use B-splines as the basis for both the design optimization and the flow analysis, thereby unifying the models for geometry and analysis, and, at the same time......The subject of this work is numerical shape optimization in fluid mechanics, based on isogeometric analysis. The generic goal is to design the shape of a 2-dimensional flow domain to minimize some prescribed objective while satisfying given geometric constraints. As part of the design problem......, facilitating a compact representation of complex geometries and smooth approximations of the flow fields. To drive the shape optimization, we use a gradient-based approach, and to avoid inappropriate parametrizations during optimization, we regularize the optimization problem by adding to the objective...
Shape Optimization of Swimming Sheets
Energy Technology Data Exchange (ETDEWEB)
Wilkening, J.; Hosoi, A.E.
2005-03-01
The swimming behavior of a flexible sheet which moves by propagating deformation waves along its body was first studied by G. I. Taylor in 1951. In addition to being of theoretical interest, this problem serves as a useful model of the locomotion of gastropods and various micro-organisms. Although the mechanics of swimming via wave propagation has been studied extensively, relatively little work has been done to define or describe optimal swimming by this mechanism.We carry out this objective for a sheet that is separated from a rigid substrate by a thin film of viscous Newtonian fluid. Using a lubrication approximation to model the dynamics, we derive the relevant Euler-Lagrange equations to optimize swimming speed and efficiency. The optimization equations are solved numerically using two different schemes: a limited memory BFGS method that uses cubic splines to represent the wave profile, and a multi-shooting Runge-Kutta approach that uses the Levenberg-Marquardt method to vary the parameters of the equations until the constraints are satisfied. The former approach is less efficient but generalizes nicely to the non-lubrication setting. For each optimization problem we obtain a one parameter family of solutions that becomes singular in a self-similar fashion as the parameter approaches a critical value. We explore the validity of the lubrication approximation near this singular limit by monitoring higher order corrections to the zeroth order theory and by comparing the results with finite element solutions of the full Stokes equations.
Conceptual shape optimization of entry vehicles applied to capsules and winged fuselage vehicles
Dirkx, Dominic
2017-01-01
This book covers the parameterization of entry capsules, including Apollo capsules and planetary probes, and winged entry vehicles such as the Space Shuttle and lifting bodies. The aerodynamic modelling is based on a variety of panel methods that take shadowing into account, and it has been validated with flight and wind tunnel data of Apollo and the Space Shuttle. The shape optimization is combined with constrained trajectory analysis, and the multi-objective approach provides the engineer with a Pareto front of optimal shapes. The method detailed in Conceptual Shape Optimization of Entry Vehicles is straightforward, and the output gives the engineer insight in the effect of shape variations on trajectory performance. All applied models and algorithms used are explained in detail, allowing for reconstructing the design tool to the researcher’s requirements. Conceptual Shape Optimization of Entry Vehicles will be of interest to both researchers and graduate students in the field of aerospace engineering, an...
Integrated Aerodynamic/Structural/Dynamic Analyses of Aircraft with Large Shape Changes
Samareh, Jamshid A.; Chwalowski, Pawel; Horta, Lucas G.; Piatak, David J.; McGowan, Anna-Maria R.
2007-01-01
The conceptual and preliminary design processes for aircraft with large shape changes are generally difficult and time-consuming, and the processes are often customized for a specific shape change concept to streamline the vehicle design effort. Accordingly, several existing reports show excellent results of assessing a particular shape change concept or perturbations of a concept. The goal of the current effort was to develop a multidisciplinary analysis tool and process that would enable an aircraft designer to assess several very different morphing concepts early in the design phase and yet obtain second-order performance results so that design decisions can be made with better confidence. The approach uses an efficient parametric model formulation that allows automatic model generation for systems undergoing radical shape changes as a function of aerodynamic parameters, geometry parameters, and shape change parameters. In contrast to other more self-contained approaches, the approach utilizes off-the-shelf analysis modules to reduce development time and to make it accessible to many users. Because the analysis is loosely coupled, discipline modules like a multibody code can be easily swapped for other modules with similar capabilities. One of the advantages of this loosely coupled system is the ability to use the medium-to high-fidelity tools early in the design stages when the information can significantly influence and improve overall vehicle design. Data transfer among the analysis modules are based on an accurate and automated general purpose data transfer tool. In general, setup time for the integrated system presented in this paper is 2-4 days for simple shape change concepts and 1-2 weeks for more mechanically complicated concepts. Some of the key elements briefly described in the paper include parametric model development, aerodynamic database generation, multibody analysis, and the required software modules as well as examples for a telescoping wing, a
Energy Technology Data Exchange (ETDEWEB)
Oliveira, P.H.I.A. de; Bortolus, M.V.; Pinto, R.L.U. de F. [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Dept. de Engenharia Mecanica
1998-07-01
This paper presents a numerical procedure to determine the optimal turbine blades geometry. It consists of the application of a non-linear algorithm on aerodynamic analysis model, developed from the Blade Element Method. Results are obtained for several tip speed ratios to determine the optimal operation condition. (author)
Optimization of the head shape of the CRH3 high speed train
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Aiming at optimizing the head shape of the CRH3 high speed train, an efficient optimization approach is proposed. The CFD analysis by solving Navier-Stokes equations is coupled with optimization calculation based on the multi-objective genetic algorithm, meanwhile the arbitrary shape deformation technique (ASD) is also introduced into the design flow, which greatly shortens the time consumption for geometry regeneration and flow field remeshing. As a result, the efficiency of the optimization calculation is highly improved. Statistical analysis is done to the designs in the design space, and the correlation between the design variables and the objective is studied to find out the key variables that most affect the objective. Response surface analysis is also performed to get the nonlinear relationship between the key design variables and the objective with the Kriging algorithm. Finally, after the optimization, an aerodynamic performance comparison between the optimal shape and the original shape reveals that the original shape of CRH3 high speed train owns a very stable aerodynamic performance and can be trustingly used in industry.
Effects of Leaders Position and Shape on Aerodynamic Performances of V Flight Formation
Thien, H P; Muhammad, H
2008-01-01
The influences of the leader in a group of V flight formation are dealt with. The investigation is focused on the effect of its position and shape on aerodynamics performances of a given V flight formation. Vortices generated the wing tip of the leader moves downstream forming a pair of opposite rotating line vortices. These vortices are generally undesirable because they create a downwash that increases the induced drag on leaders wing. However, this downwash is also accompanied by an upwash that can beneficial to the followers wing flying behind the leaders one, namely a favorable lift for the followers wing. How much contributions of the leaders wing to the followers wing in the V formation flight is determined by the strength of tip vortices generated by the leaders wing which is influenced by its position and shape including incidence angle, dihedral angle, aspect ratio and taper ratio. The prediction of aerodynamic performances of the V flight formation including lift, drag and moment coefficients is nu...
Optimal Nesting for Continuous Shape Stamping Processes
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
This paper discusses the optimal nesting problem for minimizing the scrap in continuous shape stamping processes. The shape sliding technique is used to propose a new approach, OVERLAP-and-ESCAPE, to solve the problem of continuously nesting shapes onto a metal coil of fixed or selectable width. The approach is used to construct the objective function of the mathematical model of the problem using the Simulated Annealing Algorithm to determine the globally minimal configurations for the nesting problems. Some representative cases are studied and the results are encouraging. An automatic nesting software package for manufacturing bicycle chain link blanks is also described.
Shape optimization techniques for musical instrument design
Henrique, Luis; Antunes, Jose; Carvalho, Joao S.
2002-11-01
The design of musical instruments is still mostly based on empirical knowledge and costly experimentation. One interesting improvement is the shape optimization of resonating components, given a number of constraints (allowed parameter ranges, shape smoothness, etc.), so that vibrations occur at specified modal frequencies. Each admissible geometrical configuration generates an error between computed eigenfrequencies and the target set. Typically, error surfaces present many local minima, corresponding to suboptimal designs. This difficulty can be overcome using global optimization techniques, such as simulated annealing. However these methods are greedy, concerning the number of function evaluations required. Thus, the computational effort can be unacceptable if complex problems, such as bell optimization, are tackled. Those issues are addressed in this paper, and a method for improving optimization procedures is proposed. Instead of using the local geometric parameters as searched variables, the system geometry is modeled in terms of truncated series of orthogonal space-funcitons, and optimization is performed on their amplitude coefficients. Fourier series and orthogonal polynomials are typical such functions. This technique reduces considerably the number of searched variables, and has a potential for significant computational savings in complex problems. It is illustrated by optimizing the shapes of both current and uncommon marimba bars.
Aerodynamic Drag Reduction for a Generic Truck Using Geometrically Optimized Rear Cabin Bumps
Directory of Open Access Journals (Sweden)
Abdellah Ait Moussa
2015-01-01
Full Text Available The continuous surge in gas prices has raised major concerns about vehicle fuel efficiency, and drag reduction devices offer a promising strategy. In this paper, we investigate the mechanisms by which geometrically optimized bumps, placed on the rear end of the cabin roof of a generic truck, reduce aerodynamic drag. The incorporation of these devices requires proper choices of the size, location, and overall geometry. In the following analysis we identify these factors using a novel methodology. The numerical technique combines automatic modeling of the add-ons, computational fluid dynamics and optimization using orthogonal arrays, and probabilistic restarts. Numerical results showed reduction in aerodynamic drag between 6% and 10%.
Shape Optimization Problems with Internal Constraint
Bucur, Dorin; Velichkov, Bozhidar
2011-01-01
We consider shape optimization problems with internal inclusion constraints, of the form $$\\min\\big\\{J(\\Omega)\\ :\\ \\Dr\\subset\\Omega\\subset\\R^d,\\ |\\Omega|=m\\big\\},$$ where the set $\\Dr$ is fixed, possibly unbounded, and $J$ depends on $\\Omega$ via the spectrum of the Dirichlet Laplacian. We analyze the existence of a solution and its qualitative properties, and rise some open questions.
Optimal convex shapes for concave functionals
Bucur, Dorin; Lamboley, Jimmy
2011-01-01
Motivated by a long-standing conjecture of Polya and Szeg\\"o about the Newtonian capacity of convex bodies, we discuss the role of concavity inequalities in shape optimization, and we provide several counterexamples to the Blaschke-concavity of variational functionals, including capacity. We then introduce a new algebraic structure on convex bodies, which allows to obtain global concavity and indecomposability results, and we discuss their application to isoperimetriclike inequalities. As a byproduct of this approach we also obtain a quantitative version of the Kneser-S\\"uss inequality. Finally, for a large class of functionals involving Dirichlet energies and the surface measure, we perform a local analysis of strictly convex portions of the boundary via second order shape derivatives. This allows in particular to exclude the presence of smooth regions with positive Gauss curvature in an optimal shape for Polya-Szeg\\"o problem.
Adaptive finite element method for shape optimization
Morin, Pedro
2012-01-16
We examine shape optimization problems in the context of inexact sequential quadratic programming. Inexactness is a consequence of using adaptive finite element methods (AFEM) to approximate the state and adjoint equations (via the dual weighted residual method), update the boundary, and compute the geometric functional. We present a novel algorithm that equidistributes the errors due to shape optimization and discretization, thereby leading to coarse resolution in the early stages and fine resolution upon convergence, and thus optimizing the computational effort. We discuss the ability of the algorithm to detect whether or not geometric singularities such as corners are genuine to the problem or simply due to lack of resolution - a new paradigm in adaptivity. © EDP Sciences, SMAI, 2012.
DEFF Research Database (Denmark)
Herbert-Acero, José F.; Martínez-Lauranchet, Jaime; Probst, Oliver
2014-01-01
This work presents a novel framework for the aerodynamic design and optimization of blades for small horizontal axiswind turbines (WT). The framework is based on a state-of-the-art blade element momentum model, which is complemented with the XFOIL 6.96 software in order to provide an estimate...
Elastically Shaped Wing Optimization and Aircraft Concept for Improved Cruise Efficiency
Nguyen, Nhan; Trinh, Khanh; Reynolds, Kevin; Kless, James; Aftosmis, Michael; Urnes, James, Sr.; Ippolito, Corey
2013-01-01
This paper presents the findings of a study conducted tn 2010 by the NASA Innovation Fund Award project entitled "Elastically Shaped Future Air Vehicle Concept". The study presents three themes in support of meeting national and global aviation challenges of reducing fuel burn for present and future aviation systems. The first theme addresses the drag reduction goal through innovative vehicle configurations via non-planar wing optimization. Two wing candidate concepts have been identified from the wing optimization: a drooped wing shape and an inflected wing shape. The drooped wing shape is a truly biologically inspired wing concept that mimics a seagull wing and could achieve about 5% to 6% drag reduction, which is aerodynamically significant. From a practical perspective, this concept would require new radical changes to the current aircraft development capabilities for new vehicles with futuristic-looking wings such as this concept. The inflected wing concepts could achieve between 3% to 4% drag reduction. While the drag reduction benefit may be less, the inflected-wing concept could have a near-term impact since this concept could be developed within the current aircraft development capabilities. The second theme addresses the drag reduction goal through a new concept of elastic wing shaping control. By aeroelastically tailoring the wing shape with active control to maintain optimal aerodynamics, a significant drag reduction benefit could be realized. A significant reduction in fuel burn for long-range cruise from elastic wing shaping control could be realized. To realize the potential of the elastic wing shaping control concept, the third theme emerges that addresses the drag reduction goal through a new aerodynamic control effector called a variable camber continuous trailing edge flap. Conventional aerodynamic control surfaces are discrete independent surfaces that cause geometric discontinuities at the trailing edge region. These discontinuities promote
Rapid Parameterization Schemes for Aircraft Shape Optimization
Li, Wu
2012-01-01
A rapid shape parameterization tool called PROTEUS is developed for aircraft shape optimization. This tool can be applied directly to any aircraft geometry that has been defined in PLOT3D format, with the restriction that each aircraft component must be defined by only one data block. PROTEUS has eight types of parameterization schemes: planform, wing surface, twist, body surface, body scaling, body camber line, shifting/scaling, and linear morphing. These parametric schemes can be applied to two types of components: wing-type surfaces (e.g., wing, canard, horizontal tail, vertical tail, and pylon) and body-type surfaces (e.g., fuselage, pod, and nacelle). These schemes permit the easy setup of commonly used shape modification methods, and each customized parametric scheme can be applied to the same type of component for any configuration. This paper explains the mathematics for these parametric schemes and uses two supersonic configurations to demonstrate the application of these schemes.
Optimal stimulus shapes for neuronal excitation.
Directory of Open Access Journals (Sweden)
Daniel B Forger
2011-07-01
Full Text Available An important problem in neuronal computation is to discern how features of stimuli control the timing of action potentials. One aspect of this problem is to determine how an action potential, or spike, can be elicited with the least energy cost, e.g., a minimal amount of applied current. Here we show in the Hodgkin & Huxley model of the action potential and in experiments on squid giant axons that: 1 spike generation in a neuron can be highly discriminatory for stimulus shape and 2 the optimal stimulus shape is dependent upon inputs to the neuron. We show how polarity and time course of post-synaptic currents determine which of these optimal stimulus shapes best excites the neuron. These results are obtained mathematically using the calculus of variations and experimentally using a stochastic search methodology. Our findings reveal a surprising complexity of computation at the single cell level that may be relevant for understanding optimization of signaling in neurons and neuronal networks.
Fully Optimized Shaped Pupils for Arbitrary Apertures
Carlotti, Alexis; Vanderbei, R.; Kasdin, N. J.; Che, G.
2012-01-01
Optimal apodization masks for monolithic and segmented apertures are presented, with and without central obstruction and spider vanes. Examples of optimal masks are shown for several ground-based telescopes (The Subaru, Keck, Gemini, Palomar and Very Large telescopes). We also discuss the case of extremely large telescopes. Various high-contrast regions are considered with different inner and outer working angles, shapes and contrasts. These parameters are chosen to fit the specific constraints of each instrument, in particular those set by the dedicated coronagraphic adaptive optics system. Because of the limited size of the high-contrast regions, all the masks that result from these optimizations tend to have binary transmissions, and are thus as achromatic as previous shaped pupils. Effort is put on obtaining structurally connected masks. We intend to test these new shaped pupils in Princeton's high-contrast imaging laboratory, and to this end we explore different techniques to make the masks, such as cutting them in a metal layer, laying them on a glass substrate, or using a MOEMS device.
Rajkumar, T.; Aragon, Cecilia; Bardina, Jorge; Britten, Roy
2002-01-01
A fast, reliable way of predicting aerodynamic coefficients is produced using a neural network optimized by a genetic algorithm. Basic aerodynamic coefficients (e.g. lift, drag, pitching moment) are modelled as functions of angle of attack and Mach number. The neural network is first trained on a relatively rich set of data from wind tunnel tests of numerical simulations to learn an overall model. Most of the aerodynamic parameters can be well-fitted using polynomial functions. A new set of data, which can be relatively sparse, is then supplied to the network to produce a new model consistent with the previous model and the new data. Because the new model interpolates realistically between the sparse test data points, it is suitable for use in piloted simulations. The genetic algorithm is used to choose a neural network architecture to give best results, avoiding over-and under-fitting of the test data.
Double-stage Metamodel and Its Application in Aerodynamic Design Optimization
Institute of Scientific and Technical Information of China (English)
ZHANG Dehu; GAO Zhenghong; HUANG Likeng; WANG Mingliang
2011-01-01
Constructing metamodel with global high-fidelity in design space is significant in engineering design.In this paper,a dou ble-stage metamodel(DSM)which integrates advantages of both interpolation mctamodel and regression metamodel is constructed.It takes regression model as the first stage to fit overall distribution of the original model,and then interpolation model of regression model approximation error is used as the second stage to improve accuracy.Under the same conditions and with the same samples,DSM expresses higher fidelity and represents physical characteristics of original model better.Besides,in order to validate DSM characteristics,three examples including Ackley finction,airfoil aerodynamic analysis and wing aerodynamic analysis are investigated.In the end,airfoil and wing aerodynamic design optimizations using genetic algorithm are presented to verify the engineering applicability of DSM.
Rajkumar, T.; Bardina, Jorge; Clancy, Daniel (Technical Monitor)
2002-01-01
Wind tunnels use scale models to characterize aerodynamic coefficients, Wind tunnel testing can be slow and costly due to high personnel overhead and intensive power utilization. Although manual curve fitting can be done, it is highly efficient to use a neural network to define the complex relationship between variables. Numerical simulation of complex vehicles on the wide range of conditions required for flight simulation requires static and dynamic data. Static data at low Mach numbers and angles of attack may be obtained with simpler Euler codes. Static data of stalled vehicles where zones of flow separation are usually present at higher angles of attack require Navier-Stokes simulations which are costly due to the large processing time required to attain convergence. Preliminary dynamic data may be obtained with simpler methods based on correlations and vortex methods; however, accurate prediction of the dynamic coefficients requires complex and costly numerical simulations. A reliable and fast method of predicting complex aerodynamic coefficients for flight simulation I'S presented using a neural network. The training data for the neural network are derived from numerical simulations and wind-tunnel experiments. The aerodynamic coefficients are modeled as functions of the flow characteristics and the control surfaces of the vehicle. The basic coefficients of lift, drag and pitching moment are expressed as functions of angles of attack and Mach number. The modeled and training aerodynamic coefficients show good agreement. This method shows excellent potential for rapid development of aerodynamic models for flight simulation. Genetic Algorithms (GA) are used to optimize a previously built Artificial Neural Network (ANN) that reliably predicts aerodynamic coefficients. Results indicate that the GA provided an efficient method of optimizing the ANN model to predict aerodynamic coefficients. The reliability of the ANN using the GA includes prediction of aerodynamic
On the shape optimization of flapping wings and their performance analysis
Ghommem, Mehdi
2014-01-01
The present work is concerned with the shape optimization of flapping wings in forward flight. The analysis is performed by combining a gradient-based optimizer with the unsteady vortex lattice method (UVLM). We describe the UVLM simulation procedure and provide the first methodology to select properly the mesh and time-step sizes to achieve invariant UVLM simulation results under mesh refinement. Our objective is to identify a set of optimized shapes that maximize the propulsive efficiency, defined as the ratio of the propulsive power over the aerodynamic power, under lift, thrust, and area constraints. Several parameters affecting flight performance are investigated and their impact is described. These include the wingÊ1/4s aspect ratio, camber line, and curvature of the leading and trailing edges. This study provides guidance for shape design of engineered flying systems. © 2013 Elsevier Masson SAS.
Multi-objective optimization strategies using adjoint method and game theory in aerodynamics
Institute of Scientific and Technical Information of China (English)
Zhili Tang
2006-01-01
There are currently three different game strategies originated in economics:(1) Cooperative games (Pareto front),(2)Competitive games (Nash game) and (3)Hierarchical games (Stackelberg game).Each game achieves different equilibria with different performance,and their players play different roles in the games.Here,we introduced game concept into aerodynamic design, and combined it with adjoint method to solve multicriteria aerodynamic optimization problems.The performance distinction of the equilibria of these three game strategies was investigated by numerical experiments.We computed Pareto front, Nash and Stackelberg equilibria of the same optimization problem with two conflicting and hierarchical targets under different parameterizations by using the deterministic optimization method.The numerical results show clearly that all the equilibria solutions are inferior to the Pareto front.Non-dominated Pareto front solutions are obtained,however the CPU cost to capture a set of solutions makes the Pareto front an expensive tool to the designer.
Genetic algorithms in bidisciplinary (aerodynamics/electromagnetism) optimization
Institute of Scientific and Technical Information of China (English)
朱自强; 李海明; 李津; 于日新
2001-01-01
The genetic algorithm(GA) is a non-traditional, probability search and global optimization method similar to natural selection and evolution. The key points and control parameters of this method are briefly discussed. To apply it to a multiobjective and multidisciplinary optimization problem a kind of fitness function is suggested, in which the requirements of multiobjects and multiconstraints are considered and the nondimensional coefficients and panalty coefficients of the constraint function are also introduced. Numerical results of bidisciplinary optimization calculation show that the present method is effective, applicable, and robust.
On Optimal Shapes in Materials and Structures
DEFF Research Database (Denmark)
Pedersen, Pauli
2000-01-01
In the micromechanics design of materials, as well as in the design of structural connections, the boundary shape plays an important role. The objective may be the stiffest design, the strongest design or just a design of uniform energy density along the shape. In an energy formulation it is proven...... that these three objectives have the same solution, at least within the limits of geometrical constraints, including the parametrization. Without involving stress/strain fields, the proof holds for 3D-problems, for power-law nonlinear elasticity and for anisotropic elasticity. To clarify the importance...... of parametrization, the problem of material/hole design for maximum bulk modulus is analysed. A simple optimality criterion is derived and with a simple superelliptic parametrization, agreement with Hashin-Shtrikman bounds are found. More general examples including nonequal principal strains, nonlinear elasticity...
Optimal cycling time trial position models: aerodynamics versus power output and metabolic energy.
Fintelman, D M; Sterling, M; Hemida, H; Li, F-X
2014-06-03
The aerodynamic drag of a cyclist in time trial (TT) position is strongly influenced by the torso angle. While decreasing the torso angle reduces the drag, it limits the physiological functioning of the cyclist. Therefore the aims of this study were to predict the optimal TT cycling position as function of the cycling speed and to determine at which speed the aerodynamic power losses start to dominate. Two models were developed to determine the optimal torso angle: a 'Metabolic Energy Model' and a 'Power Output Model'. The Metabolic Energy Model minimised the required cycling energy expenditure, while the Power Output Model maximised the cyclists׳ power output. The input parameters were experimentally collected from 19 TT cyclists at different torso angle positions (0-24°). The results showed that for both models, the optimal torso angle depends strongly on the cycling speed, with decreasing torso angles at increasing speeds. The aerodynamic losses outweigh the power losses at cycling speeds above 46km/h. However, a fully horizontal torso is not optimal. For speeds below 30km/h, it is beneficial to ride in a more upright TT position. The two model outputs were not completely similar, due to the different model approaches. The Metabolic Energy Model could be applied for endurance events, while the Power Output Model is more suitable in sprinting or in variable conditions (wind, undulating course, etc.). It is suggested that despite some limitations, the models give valuable information about improving the cycling performance by optimising the TT cycling position.
Aerodynamic optimization of supersonic compressor cascade using differential evolution on GPU
Aissa, Mohamed Hasanine; Verstraete, Tom; Vuik, Cornelis
2016-06-01
Differential Evolution (DE) is a powerful stochastic optimization method. Compared to gradient-based algorithms, DE is able to avoid local minima but requires at the same time more function evaluations. In turbomachinery applications, function evaluations are performed with time-consuming CFD simulation, which results in a long, non affordable, design cycle. Modern High Performance Computing systems, especially Graphic Processing Units (GPUs), are able to alleviate this inconvenience by accelerating the design evaluation itself. In this work we present a validated CFD Solver running on GPUs, able to accelerate the design evaluation and thus the entire design process. An achieved speedup of 20x to 30x enabled the DE algorithm to run on a high-end computer instead of a costly large cluster. The GPU-enhanced DE was used to optimize the aerodynamics of a supersonic compressor cascade, achieving an aerodynamic loss minimization of 20%.
Multi-Objective Aerodynamic and Structural Optimization of Horizontal-Axis Wind Turbine Blades
Directory of Open Access Journals (Sweden)
Jie Zhu
2017-01-01
Full Text Available A procedure based on MATLAB combined with ANSYS is presented and utilized for the multi-objective aerodynamic and structural optimization of horizontal-axis wind turbine (HAWT blades. In order to minimize the cost of energy (COE and improve the overall performance of the blades, materials of carbon fiber reinforced plastic (CFRP combined with glass fiber reinforced plastic (GFRP are applied. The maximum annual energy production (AEP, the minimum blade mass and the minimum blade cost are taken as three objectives. Main aerodynamic and structural characteristics of the blades are employed as design variables. Various design requirements including strain, deflection, vibration and buckling limits are taken into account as constraints. To evaluate the aerodynamic performances and the structural behaviors, the blade element momentum (BEM theory and the finite element method (FEM are applied in the procedure. Moreover, the non-dominated sorting genetic algorithm (NSGA II, which constitutes the core of the procedure, is adapted for the multi-objective optimization of the blades. To prove the efficiency and reliability of the procedure, a commercial 1.5 MW HAWT blade is used as a case study, and a set of trade-off solutions is obtained. Compared with the original scheme, the optimization results show great improvements for the overall performance of the blade.
Three-dimensional canard-wing shape optimization in aircraft cruise and maneuver environments
De Silva, B. M. E.; Carmichael, R. L.
1978-01-01
This paper demonstrates a numerical technique for canard-wing shape optimization at two operating conditions. For purposes of simplicity, a mean surface wing paneling code is employed for the aerodynamic calculations. The optimization procedures are based on the method of feasible directions. The shape functions for describing the thickness, camber, and twist are based on polynomial representations. The primary design requirements imposed restrictions on the canard and wing volumes and on the lift coefficients at the operating conditions. Results indicate that significant improvements in minimum drag and lift-to-drag ratio are possible with reasonable aircraft geometries. Calculations were done for supersonic speeds with Mach numbers ranging from 1 to 6. Planforms were mainly of a delta shape with aspect ratio of 1.
Kavvadias, I. S.; Papoutsis-Kiachagias, E. M.; Dimitrakopoulos, G.; Giannakoglou, K. C.
2015-11-01
In this article, the gradient of aerodynamic objective functions with respect to design variables, in problems governed by the incompressible Navier-Stokes equations coupled with the k-ω SST turbulence model, is computed using the continuous adjoint method, for the first time. Shape optimization problems for minimizing drag, in external aerodynamics (flows around isolated airfoils), or viscous losses in internal aerodynamics (duct flows) are considered. Sensitivity derivatives computed with the proposed adjoint method are compared to those computed with finite differences or a continuous adjoint variant based on the frequently used assumption of frozen turbulence; the latter proves the need for differentiating the turbulence model. Geometries produced by optimization runs performed with sensitivities computed by the proposed method and the 'frozen turbulence' assumption are also compared to quantify the gain from formulating and solving the adjoint to the turbulence model equations.
Aerodynamic Optimization Based on Continuous Adjoint Method for a Flexible Wing
Directory of Open Access Journals (Sweden)
Zhaoke Xu
2016-01-01
Full Text Available Aerodynamic optimization based on continuous adjoint method for a flexible wing is developed using FORTRAN 90 in the present work. Aerostructural analysis is performed on the basis of high-fidelity models with Euler equations on the aerodynamic side and a linear quadrilateral shell element model on the structure side. This shell element can deal with both thin and thick shell problems with intersections, so this shell element is suitable for the wing structural model which consists of two spars, 20 ribs, and skin. The continuous adjoint formulations based on Euler equations and unstructured mesh are derived and used in the work. Sequential quadratic programming method is adopted to search for the optimal solution using the gradients from continuous adjoint method. The flow charts of rigid and flexible optimization are presented and compared. The objective is to minimize drag coefficient meanwhile maintaining lift coefficient for a rigid and flexible wing. A comparison between the results from aerostructural analysis of rigid optimization and flexible optimization is shown here to demonstrate that it is necessary to include the effect of aeroelasticity in the optimization design of a wing.
Liu, Gao-Lian
1991-01-01
Advances in inverse design and optimization theory in engineering fields in China are presented. Two original approaches, the image-space approach and the variational approach, are discussed in terms of turbomachine aerodynamic inverse design. Other areas of research in turbomachine aerodynamic inverse design include the improved mean-streamline (stream surface) method and optimization theory based on optimal control. Among the additional engineering fields discussed are the following: the inverse problem of heat conduction, free-surface flow, variational cogeneration of optimal grid and flow field, and optimal meshing theory of gears.
Shape and topology optimization of enzymatic microreactors
DEFF Research Database (Denmark)
Pereira Rosinha, Ines
in a chemical process do not always yield in the best reaction conditions.This thesis develops an innovative application of topology and shape optimization methods to achemical engineering problem. The main goal is to design a reactor according to the limitations of the reaction system by modifying the reactor......, the enzyme is uniformly distributed inside a reactor, which can mean either at a wall surface or in a packed bed reactor or free in solution. Therefore, these three applications are studied.The aim is to improve the product formation per same amount of enzyme in the reactor. The Evolutionary Structural...... of a structure and results in the deformation of the configuration. Topologyoptimization contributes to the improvement of the layout of the material in a domain. Themechanical performance of a structure is evaluated by an objective function which can be for example maximizing its stiffness.The need...
Finding optimum airfoil shape to get maximum aerodynamic efficiency for a wind turbine
Sogukpinar, Haci; Bozkurt, Ismail
2017-02-01
In this study, aerodynamic performances of S-series wind turbine airfoil of S 825 are investigated to find optimum angle of attack. Aerodynamic performances calculations are carried out by utilization of a Computational Fluid Dynamics (CFD) method withstand finite capacity approximation by using Reynolds-Averaged-Navier Stokes (RANS) theorem. The lift and pressure coefficients, lift to drag ratio of airfoil S 825 are analyzed with SST turbulence model then obtained results crosscheck with wind tunnel data to verify the precision of computational Fluid Dynamics (CFD) approximation. The comparison indicates that SST turbulence model used in this study can predict aerodynamics properties of wind blade.
Optimization of lens shape for autostereoscopic display
Su, Ping; An, Shu; Ma, Jianshe
2016-10-01
The three-dimensional(3D) displays based on binocular parallax have drawn increasingly interests. The light splitting element, which presents separate images to the viewer's left and right eyes, plays an important part in the auto-stereoscopic display. Lenticular lenses are widely used as the light splitting elements. However, the crosstalk resulted from the unsatisfied splitting may reduce the 3D experience. It was determined that the most suitable cross sectional shape for lenticular lenses is elliptical. Firstly, the formula of the surface is derived based on the ellipse expression and the requirement of the 3D display system, that is y2+0.5651x2 - 303.4768=0. Secondly, one axial source and 4 off-axial sources placed at the heights of 2.5mm, 5mm, 7.5mm and 8mm are used to analyze the beam splitting quality of the cylindrical and elliptical lens element, respectively. The spot of elliptical lens is smaller which means a better beam splitting quality. Thirdly, Monte Carlo Non-Sequential Ray tracing algorithm is used to simulate the luminance distribution on the viewing plane, the narrower width of vertical stripes means that the aberration is suppressed. Finally, the shape of elliptical can reduce the processing difficulty with the 10μm minimum step width. In a word, the optimization of the surface has a significant effect on the improvement of stereoscopic depth and the reduction of ghost images.
Shape optimization of self-avoiding curves
Walker, Shawn W.
2016-04-01
This paper presents a softened notion of proximity (or self-avoidance) for curves. We then derive a sensitivity result, based on shape differential calculus, for the proximity. This is combined with a gradient-based optimization approach to compute three-dimensional, parameterized curves that minimize the sum of an elastic (bending) energy and a proximity energy that maintains self-avoidance by a penalization technique. Minimizers are computed by a sequential-quadratic-programming (SQP) method where the bending energy and proximity energy are approximated by a finite element method. We then apply this method to two problems. First, we simulate adsorbed polymer strands that are constrained to be bound to a surface and be (locally) inextensible. This is a basic model of semi-flexible polymers adsorbed onto a surface (a current topic in material science). Several examples of minimizing curve shapes on a variety of surfaces are shown. An advantage of the method is that it can be much faster than using molecular dynamics for simulating polymer strands on surfaces. Second, we apply our proximity penalization to the computation of ideal knots. We present a heuristic scheme, utilizing the SQP method above, for minimizing rope-length and apply it in the case of the trefoil knot. Applications of this method could be for generating good initial guesses to a more accurate (but expensive) knot-tightening algorithm.
Research on multi-fidelity aerodynamic optimization methods
Institute of Scientific and Technical Information of China (English)
Huang Likeng; Gao Zhenghong; Zhang Dehu
2013-01-01
Constructing high approximation accuracy surrogate model with lower computational cost has great engineering significance.In this paper,using co-Kriging method,an efficient multifidelity surrogate model is constructed based on two independent high and low fidelity samples.Co-Kriging method can use a greater quantity of low-fidelity information to enhance the accuracy of a surrogate of the high-fidelity model by modeling the correlation between high and low fidelity model,thus computational cost of building surrogate model can be greatly reduced.A wing-body problem is taken as an example to compare characteristics of co-Kriging multi-fidelity (CKMF)model with traditional Kriging based multi-fidelity (KMF) model.A sampling convergence of the CKMF model and the KMF model is conducted,and an appropriate sampling design is selected through the sampling convergence analysis.The results indicate that CKMF model has higher approximation accuracy with the same high-fidelity samples,and converges at less high-fidelity samples.A wing-body drag reduction optimization design using genetic algorithm is implemented.Satisfying design results are obtained,which validate the feasibility of CKMF model in engineering design.
Institute of Scientific and Technical Information of China (English)
HU Zhi-peng; LIU Rong-zhong; GUO Rui
2012-01-01
The design of terminally sensitive projectile scanning platform requires a better understanding of its aerodynamic characteristics.The terminally sensitive projectile with S-C fins has a complex aerodynamic shape,which is constructed with small length to diameter ratio cylindrical body on which two low aspect ratio fins are installed.The study focuses on the effect of fin aspect ratio on the aerodynamic characteristics.Simulation was carried on based on computational fluid dynamics(CFD) method,and the pressure distribution characteristic,drag coefficient,lift coefficient and rolling moment coefficient varying with attack angle were obtained.A free flying experimental investigation focused on the kinetic aerodynamics was made.The results show that the fins provide sufficient drag to balance the terminally sensitive projectile weight to keep it flying at low and stable speed.The lift coefficient has a negative linear varying with attack angle.The rolling moment decrease with the increase in attack angle and the decrease in wing span area.
Optimal guidance of extended trajectory shaping
Institute of Scientific and Technical Information of China (English)
Wang Hui; Lin Defu; Cheng Zhenxuan; Wang Jiang
2014-01-01
To control missile’s miss distance as well as terminal impact angle, by involving the time-to-go-nth power in the cost function, an extended optimal guidance law against a constant maneu-vering target or a stationary target is proposed using the linear quadratic optimal control theory. An extended trajectory shaping guidance (ETSG) law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile’s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.
Energy Technology Data Exchange (ETDEWEB)
Zelenyuk, Alla; Cai, Yong; Imre, Dan G.
2006-03-01
With the advert of aerosol instrumentation it has become possible to simultaneously measure individual particle mobility and vacuum aerodynamic diameters. For spherical particles these two diameters yield individual particle density. In contrast, assigning a physical meaning to the mobility or aerodynamic diameter of aspherical particles is not straightforward. This paper presents an experimental exploration of the effect of particle shape on the relationship between mobility and vacuum aerodynamic diameters. We make measurements on systems of three types: 1) Agglomerates of spheres, for which the density and the volume are known; 2) Ammonium sulfate, sodium chloride, succinic acid and lauric acid irregularly shaped particles of known density; and 3) Internally mixed particles, containing organics and ammonium sulfate, of unknown density and shape. For agglomerates of spheres we observed alignment effects in the DMA and report the first measurements of the dynamic shape factors (DSFs) in free molecular regime. We present here the first experimental determination of the DSF of ammonium sulfate particles. We find for ammonium sulfate particles a DSF that increases from 1.03 to 1.07 as particle mobility diameter increases from 160 nm to 500 nm. Three types of NaC1 particles were generated and characterized: nearly spherical particles with DSF of ~1.02; cubic with DSF that increases from 1.065 to 1.17 as particle mobility diameter increases from 200 nm to 900 nm; and compact agglomerates with DSF 1.3-1.4. Organic particles were found very nearly spherical. The data suggest that particles composed of binary mixtures of ammonium sulfate and succinic acid have lower dynamic shape factors than pure ammonium sulfate particles. However, for internally mixed ammonium sulfate and lauric acid particles we cannot distinguish between nearly spherical particles with low density and particles with DSF of 1.17.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A global optimization approach to turbine blade design based on hierarchical fair competition genetic algorithms with dynamic niche (HFCDN-GAs) coupled with Reynolds-averaged Navier-Stokes (RANS) equation is presented. In order to meet the search theory of GAs and the aerodynamic performances of turbine, Bezier curve is adopted to parameterize the turbine blade profile, and a fitness function pertaining to optimization is designed. The design variables are the control points' ordinates of characteristic polygon of Bezier curve representing the turbine blade profile. The object function is the maximum lift-drag ratio of the turbine blade. The constraint conditions take into account the leading and trailing edge metal angle, and the strength and aerodynamic performances of turbine blade. And the treatment method of the constraint conditions is the flexible penalty function. The convergence history of test function indicates that HFCDN-GAs can locate the global optimum within a few search steps and have high robustness. The lift-drag ratio of the optimized blade is 8.3% higher than that of the original one. The results show that the proposed global optimization approach is effective for turbine blade.
Optimization design of blade shapes for wind turbines
DEFF Research Database (Denmark)
Chen, Jin; Wang, Xudong; Shen, Wen Zhong;
2010-01-01
For the optimization design of wind turbines, the new normal and tangential induced factors of wind turbines are given considering the tip loss of the normal and tangential forces based on the blade element momentum theory and traditional aerodynamic model. The cost model of the wind turbines...... and the optimization design model are developed. In the optimization model, the objective is the minimum cost of energy and the design variables are the chord length, twist angle and the relative thickness. Finally, the optimization is carried out for a 2 MW blade by using this optimization design model....... The performance of blades is validated through the comparison and analysis of the results. The reduced cost shows that the optimization model is good enough for the design of wind turbines. The results give a proof for the design and research on the blades of large scale wind turbines and also establish...
Blade Parameterization and Aerodynamic Design Optimization for a 3D Transonic Compressor Rotor
Institute of Scientific and Technical Information of China (English)
Naixing Chen; Hongwu Zhang; Yanji Xu; Weiguang Huang
2007-01-01
The present paper describes an optimization methodology for aerodynamic design of turbomachinery combined with a rapid 3D blade and grid generator (RAPID3DGRID), a N.S. solver, a blade parameterization method (BPM), a gradient-based parameterization-analyzing method (GPAM), a response surface method (RSM) with zooming algorithm and a simple gradient method. By the use of blade parameterization method a transonic compressor rotor can be expressed by a set of polynomials, and then it enables us to transform coordinate-expressed blade data to parameter-expressed and then to reduce the number of parameters. With changing any one of the parameters and by applying grid generator and N.S. solver, we can obtain several groups of samples. Here only ten parameters were considered to search an optimized compressor rotor. As a result of optimization, the adiabatic efficiency was increased by 1.73%.
Oloso, Amidu Olawale
A hybrid automatic differentiation/incremental iterative method was implemented in the general purpose advanced computational fluid dynamics code (CFL3D Version 4.1) to yield a new code (CFL3D.ADII) that is capable of computing consistently discrete first order sensitivity derivatives for complex geometries. With the exception of unsteady problems, the new code retains all the useful features and capabilities of the original CFL3D flow analysis code. The superiority of the new code over a carefully applied method of finite-differences is demonstrated. A coarse grain, scalable, distributed-memory, parallel version of CFL3D.ADII was developed based on "derivative stripmining". In this data-parallel approach, an identical copy of CFL3D.ADII is executed on each processor with different derivative input files. The effect of communication overhead on the overall parallel computational efficiency is negligible. However, the fraction of CFL3D.ADII duplicated on all processors has significant impact on the computational efficiency. To reduce the large execution time associated with the sequential 1-D line search in gradient-based aerodynamic optimization, an alternative parallel approach was developed. The execution time of the new approach was reduced effectively to that of one flow analysis, regardless of the number of function evaluations in the 1-D search. The new approach was found to yield design results that are essentially identical to those obtained from the traditional sequential approach but at much smaller execution time. The parallel CFL3D.ADII and the parallel 1-D line search are demonstrated in shape improvement studies of a realistic High Speed Civil Transport (HSCT) wing/body configuration represented by over 100 design variables and 200,000 grid points in inviscid supersonic flow on the 16 node IBM SP2 parallel computer at the Numerical Aerospace Simulation (NAS) facility, NASA Ames Research Center. In addition to making the handling of such a large
Takemiya, Tetsushi
, and that (2) the AMF terminates optimization erroneously when the optimization problems have constraints. The first problem is due to inaccuracy in computing derivatives in the AMF, and the second problem is due to erroneous treatment of the trust region ratio, which sets the size of the domain for an optimization in the AMF. In order to solve the first problem of the AMF, automatic differentiation (AD) technique, which reads the codes of analysis models and automatically generates new derivative codes based on some mathematical rules, is applied. If derivatives are computed with the generated derivative code, they are analytical, and the required computational time is independent of the number of design variables, which is very advantageous for realistic aerospace engineering problems. However, if analysis models implement iterative computations such as computational fluid dynamics (CFD), which solves system partial differential equations iteratively, computing derivatives through the AD requires a massive memory size. The author solved this deficiency by modifying the AD approach and developing a more efficient implementation with CFD, and successfully applied the AD to general CFD software. In order to solve the second problem of the AMF, the governing equation of the trust region ratio, which is very strict against the violation of constraints, is modified so that it can accept the violation of constraints within some tolerance. By accepting violations of constraints during the optimization process, the AMF can continue optimization without terminating immaturely and eventually find the true optimum design point. With these modifications, the AMF is referred to as "Robust AMF," and it is applied to airfoil and wing aerodynamic design problems using Euler CFD software. The former problem has 21 design variables, and the latter 64. In both problems, derivatives computed with the proposed AD method are first compared with those computed with the finite
Dose-shaping using targeted sparse optimization
Energy Technology Data Exchange (ETDEWEB)
Sayre, George A.; Ruan, Dan [Department of Radiation Oncology, University of California - Los Angeles School of Medicine, 200 Medical Plaza, Los Angeles, California 90095 (United States)
2013-07-15
's spatial dose distribution than conventional objective functions. In particular, E{sub tot}{sup sparse}-optimized plans for the pancreas case and head-and-neck case exhibited substantially improved sparing of the spinal cord and parotid glands, respectively, while maintaining or improving sparing for other OARs and markedly improving PTV homogeneity. Plan deliverability for E{sub tot}{sup sparse}-optimized plans was shown to be better than their associated clinical plans, according to the two-dimensional modulation index.Conclusions: These results suggest that our formulation may be used to improve dose-shaping and OAR-sparing for complicated disease sites, such as the pancreas or head and neck. Furthermore, our objective function and constraints are linear and constitute a linear program, which converges to the global minimum quickly, and can be easily implemented in treatment planning software. Thus, the authors expect fast translation of our method to the clinic where it may have a positive impact on plan quality for challenging disease sites.
Aerodynamic control of bridge cables through shape modification: A preliminary study
DEFF Research Database (Denmark)
Kleissl, Kenneth; Georgakis, Christos
2011-01-01
to suffer from either dry inclined galloping, ‘‘drag crisis’’ or Den Hartog galloping, the shrouded cylinder is found to be stable for all angles of attack, albeit with an increase in drag at typical design wind velocities. Finally, turbulent flow is found to introduce an increased amount of aerodynamic...
多变量气动设计问题分层协同优化%Multivariable Aerodynamic Design Based on Multilevel Collaborative Optimization
Institute of Scientific and Technical Information of China (English)
李焦赞; 高正红
2013-01-01
In future aircraft design, the desired performance indexes are not only more rigorous, but also more numerous. Therefore, aerodynamic design should achieve high definition shape design and satisfy the multiple design requirements. It is consequently necessary to establish a multivariable optimization model in aerodynamic design. In this paper, a test example is provided to show the advantage and disadvantage of the multivariable model in aerodynamic optimization. While the optimized results are significantly heightened, searching difficulty also increases for the optimization algorithm. Meanwhile, because of the coupling disturbance among different design parameters, it is difficult to achieve global optimized results. So in this paper a sampling mean-response sensitivity analysis is carried out to measure the importance of design parameters, which are then grouped based on their importance level. Subsequently the multilevel collaborative optimization design method based on system decomposition is used to reduce the system complicacy. It ensures the precision of the multivariable optimization model and resolves the searching difficulty of the optimization algorithm. An example for a wing-body optimization is carried out using the above method and the result shows its feasibility and advantage as compared with the traditional aerodynamic optimization method.%通过验证实例分析,气动设计中精细化优化模型对设计结果收敛精度的提高有很大帮助,但同时也带来优化算法搜索困难的问题,并且由于不同类型设计变量之间的相互耦合干扰使优化难以收敛到全局最优解.于是提出基于响应均值灵敏度的概念对大规模的设计变量进行重要性分组的策略,依据设计变量分组情况应用系统分解思想对多变量设计问题进行分层协同优化来降低系统的复杂度,这既保证了精细化设计的要求,又缓解了优化算法对大规模问题搜索困难的问题.与传统
Shahzad, Aamer; Tian, Fang-Bao; Young, John; Lai, Joseph C. S.
2016-11-01
This numerical study is focused on assessing the effect on the aerodynamic hovering performance of wing shapes defined by the radius of the first moment of the wing area ( r 1 ¯ ) and aspect ratio (AR). In addition, the effect of introducing a deviation angle in the kinematics is examined. The performance of r 1 ¯ = 0 . 43 , 0.53, and 0.63 wings with AR of 1.5, 2.96, 4.5, and 6.0 is investigated at Reynolds numbers (Re) = 12, 400, and 13 500. The performance trends of the wing shapes have been observed to be independent of Re for both 2-angle and 3-angle kinematics. This is because high suction pressures associated with the leading-edge vortex are predominantly spread in the distal (away from the wing root) and leeward regions (towards the trailing-edge) of high flapping velocities for all the cases. While the deviation angle is detrimental to the production of lift and power economy (PE, defined as the ratio of the mean lift coefficient to the mean aerodynamic power coefficient) at Re = 12 due to strong viscous effects, it improves PE at Re = 400 and 13 500. A high instantaneous angle of attack at the stroke reversal results in high lift peak for 3-angle kinematics but its effect at Re = 400 and 13 500 is attenuated by strong vortical structures on the underside of the wing. Maximum PE is achieved at AR = 2.96, as a low AR wing does not produce enough lift and high AR wings consume more aerodynamic power. Although the lift is maximized using high r 1 ¯ and AR wings, our results show that low r 1 ¯ and high AR wings are best for maximizing PE for a given lift in insects.
Application of Aerodynamic Shape Deformation based on NURBS Surface%NURBS曲面在气动外形变形中的应用
Institute of Scientific and Technical Information of China (English)
马晓永; 张彦军; 雷武涛
2014-01-01
针对翼吊布局飞机复杂气动外形，建立了基于样条（NURBS，非均匀有理B样条）曲面和曲面叠加技术的曲面变形方法。在对样条曲线性质分析的基础上，以DLR-F6飞机为实例，对其机翼翼根、短舱挂架局部进行曲面网格变形，结果表明该方法能有效表述其复杂几何外形及型面变化特性，并且具有较好的局域性、可控性和光滑性。该方法可有效应用于吊舱挂架等复杂气动外形的建模、表面网格变形及气动外形优化设计等。%A free deformation method based on the B-Spline (NURBS, Non-Uniform Rational B-Spline) and surface superposition technique was presented for complex aerodynamic shape such as wing mounted nacelle-pylon conifguration. The characteristic of parameters were analyzed with B-Spline curves case, and the application instances of surface grids deformation on wing and pylon of DLR-F6 plane shows that the method could describe complex surfaces and its deformation characteristic effectively, the control parameter only change its local surface, and it is easy to carry out. The method is feasible and applicable to model representation, surface grids deformation and aerodynamic shape optimization etc.
A new non-linear vortex lattice method:Applications to wing aerodynamic optimizations
Institute of Scientific and Technical Information of China (English)
Oliviu S? ugar Gabor; Andreea Koreanschi; Ruxandra Mihaela Botez
2016-01-01
This paper presents a new non-linear formulation of the classical Vortex Lattice Method (VLM) approach for calculating the aerodynamic properties of lifting surfaces. The method accounts for the effects of viscosity, and due to its low computational cost, it represents a very good tool to perform rapid and accurate wing design and optimization procedures. The mathematical model is constructed by using two-dimensional viscous analyses of the wing span-wise sections, according to strip theory, and then coupling the strip viscous forces with the forces generated by the vortex rings distributed on the wing camber surface, calculated with a fully three-dimensional vortex lifting law. The numerical results obtained with the proposed method are validated with experimental data and show good agreement in predicting both the lift and pitching moment, as well as in predicting the wing drag. The method is applied to modifying the wing of an Unmanned Aerial System to increase its aerodynamic efficiency and to calculate the drag reductions obtained by an upper surface morphing technique for an adaptable regional aircraft wing.
A new non-linear vortex lattice method: Applications to wing aerodynamic optimizations
Directory of Open Access Journals (Sweden)
Oliviu Şugar Gabor
2016-10-01
Full Text Available This paper presents a new non-linear formulation of the classical Vortex Lattice Method (VLM approach for calculating the aerodynamic properties of lifting surfaces. The method accounts for the effects of viscosity, and due to its low computational cost, it represents a very good tool to perform rapid and accurate wing design and optimization procedures. The mathematical model is constructed by using two-dimensional viscous analyses of the wing span-wise sections, according to strip theory, and then coupling the strip viscous forces with the forces generated by the vortex rings distributed on the wing camber surface, calculated with a fully three-dimensional vortex lifting law. The numerical results obtained with the proposed method are validated with experimental data and show good agreement in predicting both the lift and pitching moment, as well as in predicting the wing drag. The method is applied to modifying the wing of an Unmanned Aerial System to increase its aerodynamic efficiency and to calculate the drag reductions obtained by an upper surface morphing technique for an adaptable regional aircraft wing.
Two-Dimensional High-Lift Aerodynamic Optimization Using Neural Networks
Greenman, Roxana M.
1998-01-01
The high-lift performance of a multi-element airfoil was optimized by using neural-net predictions that were trained using a computational data set. The numerical data was generated using a two-dimensional, incompressible, Navier-Stokes algorithm with the Spalart-Allmaras turbulence model. Because it is difficult to predict maximum lift for high-lift systems, an empirically-based maximum lift criteria was used in this study to determine both the maximum lift and the angle at which it occurs. The 'pressure difference rule,' which states that the maximum lift condition corresponds to a certain pressure difference between the peak suction pressure and the pressure at the trailing edge of the element, was applied and verified with experimental observations for this configuration. Multiple input, single output networks were trained using the NASA Ames variation of the Levenberg-Marquardt algorithm for each of the aerodynamic coefficients (lift, drag and moment). The artificial neural networks were integrated with a gradient-based optimizer. Using independent numerical simulations and experimental data for this high-lift configuration, it was shown that this design process successfully optimized flap deflection, gap, overlap, and angle of attack to maximize lift. Once the neural nets were trained and integrated with the optimizer, minimal additional computer resources were required to perform optimization runs with different initial conditions and parameters. Applying the neural networks within the high-lift rigging optimization process reduced the amount of computational time and resources by 44% compared with traditional gradient-based optimization procedures for multiple optimization runs.
Shape optimization of the modular press body
Directory of Open Access Journals (Sweden)
Pabiszczak Stanisław
2016-12-01
Full Text Available A paper contains an optimization algorithm of cross-sectional dimensions of a modular press body for the minimum mass criterion. Parameters of the wall thickness and the angle of their inclination relative to the base of section are assumed as the decision variables. The overall dimensions are treated as a constant. The optimal values of parameters were calculated using numerical method of the tool Solver in the program Microsoft Excel. The results of the optimization procedure helped reduce body weight by 27% while maintaining the required rigidity of the body.
Discrete Geometry Toolkit for Shape Optimization Project
National Aeronautics and Space Administration — Simulation-based design optimization has been steadily maturing over the past two decades, but not without its own unique and persistent challenges. The proposed...
Optimal Aerodynamic Design of Conventional and Coaxial Helicopter Rotors in Hover and Forward Flight
Giovanetti, Eli B.
This dissertation investigates the optimal aerodynamic performance and design of conventional and coaxial helicopters in hover and forward flight using conventional and higher harmonic blade pitch control. First, we describe a method for determining the blade geometry, azimuthal blade pitch inputs, optimal shaft angle (rotor angle of attack), and division of propulsive and lifting forces among the components that minimize the total power for a given forward flight condition. The optimal design problem is cast as a variational statement that is discretized using a vortex lattice wake to model inviscid forces, combined with two-dimensional drag polars to model profile losses. The resulting nonlinear constrained optimization problem is solved via Newton iteration. We investigate the optimal design of a compound vehicle in forward flight comprised of a coaxial rotor system, a propeller, and optionally, a fixed wing. We show that higher harmonic control substantially reduces required power, and that both rotor and propeller efficiencies play an important role in determining the optimal shaft angle, which in turn affects the optimal design of each component. Second, we present a variational approach for determining the optimal (minimum power) torque-balanced coaxial hovering rotor using Blade Element Momentum Theory including swirl. We show that the optimal hovering coaxial rotor generates only a small percentage of its total thrust on the portion of the lower rotor operating in the upper rotor's contracted wake, resulting in an optimal design with very different upper and lower rotor twist and chord distributions. We also show that the swirl component of induced velocity has a relatively small effect on rotor performance at the disk loadings typical of helicopter rotors. Third, we describe a more refined model of the wake of a hovering conventional or coaxial rotor. We approximate the rotor or coaxial rotors as actuator disks (though not necessarily uniformly loaded
ISOGEOMETRIC SHAPE OPTIMIZATION FOR ELECTROMAGNETIC SCATTERING PROBLEMS
DEFF Research Database (Denmark)
Nguyen, D. M.; Evgrafov, Anton; Gravesen, Jens
2012-01-01
We consider the benchmark problem of magnetic energy density enhancement in a small spatial region by varying the shape of two symmetric conducting scatterers. We view this problem as a prototype for a wide variety of geometric design problems in electromagnetic applications. Our approach...
Topology and boundary shape optimization as an integrated design tool
Bendsoe, Martin Philip; Rodrigues, Helder Carrico
1990-01-01
The optimal topology of a two dimensional linear elastic body can be computed by regarding the body as a domain of the plane with a high density of material. Such an optimal topology can then be used as the basis for a shape optimization method that computes the optimal form of the boundary curves of the body. This results in an efficient and reliable design tool, which can be implemented via common FEM mesh generator and CAD type input-output facilities.
The Multipoint Global Shape Optimization of Flying Configuration with Movable Leading Edges Flaps
Directory of Open Access Journals (Sweden)
Adriana NASTASE
2012-12-01
Full Text Available The aerodynamical global optimized (GO shape of flying configuration (FC, at two cruising Mach numbers, can be realized by morphing. Movable leading edge flaps are used for this purpose. The equations of the surfaces of the wing, of the fuselage and of the flaps in stretched position are approximated in form of superpositions of homogeneous polynomes in two variables with free coefficients. These coefficients together with the similarity parameters of the planform of the FC are the free parameters of the global optimization. Two enlarged variational problems with free boundaries occur. The first one consists in the determination of the GO shape of the wing-fuselageFC, with the flaps in retracted position, which must be of minimum drag, at higher cruising Mach number. The second enlarged variational problem consists in the determination of the GO shape of the flaps in stretched position in such a manner that the entire FC shall be of minimum drag at the second lower Mach number. The iterative optimum-optimorum (OO theory of the author is used for the solving of these both enlarged variational problems. The inviscid GO shape of the FC is used only in the first step of iteration and the own developed hybrid solutions for the compressible Navier-Stokes partial-differential equations (PDEs are used for the determination of the friction drag coefficient and up the second step of iteration of OO theory.
Isogeometric shape optimization of magnetic density separators
2013-01-01
Purpose: The waste recycling industry increasingly relies on magnetic density separators. These devices generate an upward magnetic force in ferro-fluids allowing to separate the immersed particles according to their mass density. Recently a new separator design that significantly reduces the required amount of permanent magnet material has been proposed. The purpose of this paper is to alleviate the undesired end-effects in this design by altering the shape of the ferromagnetic covers of the...
Shape Optimization of an Hydrofoil by Isogeometric Analysis
Simeoni, Matthieu Martin Jean-Andre
2014-01-01
We use Isogeometric Analysis as a framework for NURBS-based shape optimization of hydrofoils. We present geometrical representations by NURBS and some of their properties to design an hydrofoil. Then, we consider an irrotational flow around an hydrofoil and solve the Laplace equation in the stream function formulation. Finally, we perform the shape optimization of the hydrofoil by considering the stream function formulation as the state problem and different objective functionals.
Laboratory Transferability of Optimally Shaped Laser Pulses for Quantum Control
Tibbetts, Katharine Moore; Rabitz, Herschel
2013-01-01
Optimal control experiments can readily identify effective shaped laser pulses, or "photonic reagents", that achieve a wide variety of objectives. For many practical applications, an important criterion is that a particular photonic reagent prescription still produce a good, if not optimal, target objective yield when transferred to a different system or laboratory, {even if the same shaped pulse profile cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments.} First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found...
Shape flows for spectral optimization problems
Bucur, Dorin; Stefanelli, Ulisse
2011-01-01
We consider a general formulation of gradient flow evolution for problems whose natural framework is the one of metric spaces. The applications we deal with are concerned with the evolution of {\\it capacitary measures} with respect to the $\\gamma$-convergence dissipation distance and with the evolution of domains in spectral optimization problems.
Reentry-Vehicle Shape Optimization Using a Cartesian Adjoint Method and CAD Geometry
Nemec, Marian; Aftosmis, Michael J.
2006-01-01
A DJOINT solutions of the governing flow equations are becoming increasingly important for the development of efficient analysis and optimization algorithms. A well-known use of the adjoint method is gradient-based shape. Given an objective function that defines some measure of performance, such as the lift and drag functionals, its gradient is computed at a cost that is essentially independent of the number of design variables (e.g., geometric parameters that control the shape). Classic aerodynamic applications of gradient-based optimization include the design of cruise configurations for transonic and supersonic flow, as well as the design of high-lift systems. are perhaps the most promising approach for addressing the issues of flow solution automation for aerodynamic design problems. In these methods, the discretization of the wetted surface is decoupled from that of the volume mesh. This not only enables fast and robust mesh generation for geometry of arbitrary complexity, but also facilitates access to geometry modeling and manipulation using parametric computer-aided design (CAD). In previous work on Cartesian adjoint solvers, Melvin et al. developed an adjoint formulation for the TRANAIR code, which is based on the full-potential equation with viscous corrections. More recently, Dadone and Grossman presented an adjoint formulation for the two-dimensional Euler equations using a ghost-cell method to enforce the wall boundary conditions. In Refs. 18 and 19, we presented an accurate and efficient algorithm for the solution of the adjoint Euler equations discretized on Cartesian meshes with embedded, cut-cell boundaries. Novel aspects of the algorithm were the computation of surface shape sensitivities for triangulations based on parametric-CAD models and the linearization of the coupling between the surface triangulation and the cut-cells. The accuracy of the gradient computation was verified using several three-dimensional test cases, which included design
Integration of dynamic, aerodynamic and structural optimization of helicopter rotor blades
Peters, David A.
1987-01-01
The purpose of the research is to study the integration of structural, dynamic, and aerodynamic considerations in the design-optimization process for helicopter rotorblades. This is to be done in three phases. Task 1 is to bring on-line computer codes that could perform the finite-element frequency analyses of rotor blades. The major features of this program are summarized. The second task was to bring on-line an optimization code for the work. Several were tried and it was decided to use CONMIN. Explicit volume constraints on the thicknesses and lumped masses used in the optimization were added. The specific aeroelastic constraint that the center of mass must be forward of the quarter chord in order to prevent flutter was applied. The bending-torsion coupling due to cg-ea offset within the blade cross section was included. Also included were some very simple stress constraints. The first three constraints are completed, and the fourth constraint is being completed.
Optimal embedding for shape indexing in medical image databases.
Qian, Xiaoning; Tagare, Hemant D; Fulbright, Robert K; Long, Rodney; Antani, Sameer
2010-06-01
This paper addresses the problem of indexing shapes in medical image databases. Shapes of organs are often indicative of disease, making shape similarity queries important in medical image databases. Mathematically, shapes with landmarks belong to shape spaces which are curved manifolds with a well defined metric. The challenge in shape indexing is to index data in such curved spaces. One natural indexing scheme is to use metric trees, but metric trees are prone to inefficiency. This paper proposes a more efficient alternative. We show that it is possible to optimally embed finite sets of shapes in shape space into a Euclidean space. After embedding, classical coordinate-based trees can be used for efficient shape retrieval. The embedding proposed in the paper is optimal in the sense that it least distorts the partial Procrustes shape distance. The proposed indexing technique is used to retrieve images by vertebral shape from the NHANES II database of cervical and lumbar spine X-ray images maintained at the National Library of Medicine. Vertebral shape strongly correlates with the presence of osteophytes, and shape similarity retrieval is proposed as a tool for retrieval by osteophyte presence and severity. Experimental results included in the paper evaluate (1) the usefulness of shape similarity as a proxy for osteophytes, (2) the computational and disk access efficiency of the new indexing scheme, (3) the relative performance of indexing with embedding to the performance of indexing without embedding, and (4) the computational cost of indexing using the proposed embedding versus the cost of an alternate embedding. The experimental results clearly show the relevance of shape indexing and the advantage of using the proposed embedding.
Mixed finite element formulation applied to shape optimization
Rodrigues, Helder; Taylor, John E.; Kikuchi, Noboru
1988-01-01
The development presented introduces a general form of mixed formulation for the optimal shape design problem. The associated optimality conditions are easily obtained without resorting to highly elaborate mathematical developments. Also, the physical significance of the adjoint problem is clearly defined with this formulation.
Iso-geometric shape optimization of magnetic density separators
DEFF Research Database (Denmark)
Dang Manh, Nguyen; Evgrafov, Anton; Gravesen, Jens;
2014-01-01
covers with B-splines and defines a cost functional that measures the non-uniformity of the magnetic field in an area above the poles. The authors apply an iso-geometric shape optimization procedure, which allows us to accurately represent, analyze and optimize the geometry using only a few design...
Lattice Boltzmann method for shape optimization of fluid distributor
Wang, Limin; Luo, Lingai
2013-01-01
This paper presents the shape optimization of a flat-type arborescent fluid distributor for the purpose of process intensification. A shape optimization algorithm based on the lattice Boltzmann method (LBM) is proposed with the objective of decreasing the flow resistance of such distributor at the constraint of constant fluid volume. Prototypes of the initial distributor as well as the optimized one are designed. Fluid distribution and hydraulic characteristics of these distributors are investigated numerically. Results show that the pressure drop of the optimized distributor is between 15.9% and 25.1% lower than that of the initial reference while keeping a uniform flow distribution, demonstrating the process intensification in fluid distributor, and suggesting the interests of the proposed optimization algorithm in engineering optimal design.
Shape optimization of high-speed penetrators: a review
Ben-Dor, Gabi; Dubinsky, Anatoly; Elperin, Tov
2012-12-01
In spite of a large number of publications on shape optimization of penetrating projectiles there are no dedicated surveys of these studies. The goal of the present review is to close this gap. The review includes more than 50 studies published since 1980 and devoted to solving particular problems of shape optimization of high-speed penetrators. We analyze publications which employed analytical and numerical method for shape optimization of high-speed penetrators against concrete, metal, fiber-reinforced plastic laminate and soil shields. We present classification of the mathematical models used for describing interaction between a penetrator and a shield. The reviewed studies are summarized in the table where we display the following information: the model; indicate whether the model accounts for or neglects friction at the surface of penetrator; criterion for optimization (depth of penetration into a semi-infinite shield, ballistic limit velocity for a shield having a finite thickness, several criteria); class of considered shapes of penetrators (bodies of revolution, different classes of 3-D bodies, etc.); method of solution (analytical or numerical); in comments we present additional information on formulation of the optimization problem. The survey also includes discussion on certain methodological facets in formulating shape optimization problems for high-speed penetrators.
National Aeronautics and Space Administration — In rotorcraft flight dynamics, optimized warping camber/twist change is a potentially enabling technology for improved overall rotorcraft performance. Recent...
A Preconditioning Method for Shape Optimization Governed by the Euler Equations
Arian, Eyal; Vatsa, Veer N.
1998-01-01
We consider a classical aerodynamic shape optimization problem subject to the compressible Euler flow equations. The gradient of the cost functional with respect to the shape variables is derived with the adjoint method at the continuous level. The Hessian (second order derivative of the cost functional with respect to the shape variables) is approximated also at the continuous level, as first introduced by Arian and Ta'asan (1996). The approximation of the Hessian is used to approximate the Newton step which is essential to accelerate the numerical solution of the optimization problem. The design space is discretized in the maximum dimension, i.e., the location of each point on the intersection of the computational mesh with the airfoil is taken to be an independent design variable. We give numerical examples for 86 design variables in two different flow speeds and achieve an order of magnitude reduction in the cost functional at a computational effort of a full solution of the analysis partial differential equation (PDE).
Shape optimization of a sodium cooled fast reactor
Schmitt, Damien; Allaire, Grégoire; Pantz, Olivier; Pozin, Nicolas
2014-06-01
Traditional designs of sodium cooled fast reactors have a positive sodium expansion feedback. During a loss of flow transient without scram, sodium heating and boiling thus insert a positive reactivity and prevents the power from decreasing. Recent studies led at CEA, AREVA and EDF show that cores with complex geometries can feature a very low or even a negative sodium void worth.(1, 2) Usual optimization methods for core conception are based on a parametric description of a given core design(3).(4) New core concepts and shapes can then only be found by hand. Shape optimization methods have proven very efficient in the conception of optimal structures under thermal or mechanical constraints.(5, 6) First studies show that these methods could be applied to sodium cooled core conception.(7) In this paper, a shape optimization method is applied to the conception of a sodium cooled fast reactor core with low sodium void worth. An objective function to be minimized is defined. It includes the reactivity change induced by a 1% sodium density decrease. The optimization variable is a displacement field changing the core geometry from one shape to another. Additionally, a parametric optimization of the plutonium content distribution of the core is made, so as to ensure that the core is kept critical, and that the power shape is flat enough. The final shape obtained must then be adjusted to a get realistic core layout. Its caracteristics can be checked with reference neutronic codes such as ERANOS. Thanks to this method, new shapes of reactor cores could be inferred, and lead to new design ideas.
Computational Aerodynamic Analysis of Three-Dimensional Ice Shapes on a NACA 23012 Airfoil
Jun, GaRam; Oliden, Daniel; Potapczuk, Mark G.; Tsao, Jen-Ching
2014-01-01
The present study identifies a process for performing computational fluid dynamic calculations of the flow over full three-dimensional (3D) representations of complex ice shapes deposited on aircraft surfaces. Rime and glaze icing geometries formed on a NACA23012 airfoil were obtained during testing in the NASA Glenn Research Centers Icing Research Tunnel (IRT). The ice shape geometries were scanned as a cloud of data points using a 3D laser scanner. The data point clouds were meshed using Geomagic software to create highly accurate models of the ice surface. The surface data was imported into Pointwise grid generation software to create the CFD surface and volume grids. It was determined that generating grids in Pointwise for complex 3D icing geometries was possible using various techniques that depended on the ice shape. Computations of the flow fields over these ice shapes were performed using the NASA National Combustion Code (NCC). Results for a rime ice shape for angle of attack conditions ranging from 0 to 10 degrees and for freestream Mach numbers of 0.10 and 0.18 are presented. For validation of the computational results, comparisons were made to test results from rapid-prototype models of the selected ice accretion shapes, obtained from a separate study in a subsonic wind tunnel at the University of Illinois at Urbana-Champaign. The computational and experimental results were compared for values of pressure coefficient and lift. Initial results show fairly good agreement for rime ice accretion simulations across the range of conditions examined. The glaze ice results are promising but require some further examination.
An improved adaptive sampling and experiment design method for aerodynamic optimization
Institute of Scientific and Technical Information of China (English)
Huang Jiangtao; Gao Zhenghong; Zhou Zhu; Zhao Ke
2015-01-01
Experiment design method is a key to construct a highly reliable surrogate model for numerical optimization in large-scale project. Within the method, the experimental design criterion directly affects the accuracy of the surrogate model and the optimization efficient. According to the shortcomings of the traditional experimental design, an improved adaptive sampling method is pro-posed in this paper. The surrogate model is firstly constructed by basic sparse samples. Then the supplementary sampling position is detected according to the specified criteria, which introduces the energy function and curvature sampling criteria based on radial basis function (RBF) network. Sampling detection criteria considers both the uniformity of sample distribution and the description of hypersurface curvature so as to significantly improve the prediction accuracy of the surrogate model with much less samples. For the surrogate model constructed with sparse samples, the sample uniformity is an important factor to the interpolation accuracy in the initial stage of adaptive sam-pling and surrogate model training. Along with the improvement of uniformity, the curvature description of objective function surface gradually becomes more important. In consideration of these issues, crowdness enhance function and root mean square error (RMSE) feedback function are introduced in C criterion expression. Thus, a new sampling method called RMSE and crowd-ness enhance (RCE) adaptive sampling is established. The validity of RCE adaptive sampling method is studied through typical test function firstly and then the airfoil/wing aerodynamic opti-mization design problem, which has high-dimensional design space. The results show that RCE adaptive sampling method not only reduces the requirement for the number of samples, but also effectively improves the prediction accuracy of the surrogate model, which has a broad prospects for applications.
On Shape Optimization for an Evolution Coupled System
Energy Technology Data Exchange (ETDEWEB)
Leugering, G., E-mail: leugering@am.uni-erlangen.de [University of Erlangen Nuremberg, Department of Mathematics (Germany); Novotny, A. A., E-mail: novotny@lncc.br; Perla Menzala, G., E-mail: perla@lncc.br [Coordenacao de Matematica Aplicada e Computacional, Laboratorio Nacional de Computacao Cientifica LNCC/MCT (Brazil); Sokolowski, J., E-mail: Jan.Sokolowski@iecn.u-nancy.fr [Institut Elie Cartan, UMR 7502 (Nancy Universite, CNRS, INRIA), Laboratoire de Mathematiques, Universite Henri Poincare Nancy I (France)
2011-12-15
A shape optimization problem in three spatial dimensions for an elasto-dynamic piezoelectric body coupled to an acoustic chamber is introduced. Well-posedness of the problem is established and first order necessary optimality conditions are derived in the framework of the boundary variation technique. In particular, the existence of the shape gradient for an integral shape functional is obtained, as well as its regularity, sufficient for applications e.g. in modern loudspeaker technologies. The shape gradients are given by functions supported on the moving boundaries. The paper extends results obtained by the authors in (Math. Methods Appl. Sci. 33(17):2118-2131, 2010) where a similar problem was treated without acoustic coupling.
Existence and approximation results for shape optimization problems in rotordynamics
Strauß, Frank; Heuveline, Vincent; Schweizer, Ben
2006-01-01
We consider a shape optimization problem in rotordynamics where the mass of a rotor is minimized subject to constraints on the natural frequencies. Our analysis is based on a class of rotors described by a Rayleigh beam model including effects of rotary inertia and gyroscopic moments. The solution of the equation of motion leads to a generalized eigenvalue problem. The governing operators are non-symmetric due to the gyroscopic terms. We prove the existence of solutions for the optimization p...
Parametric Study and Optimization of Ceiling Fan Blades for Improved Aerodynamic Performance
Directory of Open Access Journals (Sweden)
Ehsan Adeeb
2016-01-01
Full Text Available This paper includes parametric study and optimization of non-linear ceiling fan blades by combining the techniques of Design of Experiments (DOE, Response Surface Methods (RSM and Computational Fluid Dynamics (CFD. Specifically, the nonlinear (elliptical planform shape of ceiling fan blade is investigated in conjunction with blade tip width, root and tip angle of attack. Sixteen cases are designed for three blade ceiling fan using two level full factorial model. The flow field is modeled using Reynolds-Averaged-Navier-Stokes approach. The performance variables used to formulate a multi-objective optimization problem are volumetric flow rate, torque and energy efficiency. Response Surface Method is used to generate the optimized design for non-linear ceiling fan blade profile. The results reveal that the interactions between the design variables play a significant role in determining the performance. It is concluded that the nonlinear forward sweep has a moderate effect on response parameters.
Shape Assignment by Genetic Algorithm towards Designing Optimal Areas
Directory of Open Access Journals (Sweden)
Ismadi Md Badarudin
2010-07-01
Full Text Available This paper presents a preliminary study on space allocation focusing on the rectangular shapes to be assigned into an area with an intention to find optimal combination of shapes. The proposed solution is vital for promoting an optimal planting area and eventually finds the optimal number of trees as the ultimate goal. Thus, the evolutionary algorithm by GA technique was performed to find the objective. GAs by implementing some metaheuristic approaches is one of the most common techniques for handling ambiguous and / or vast possible solutions. The shape assignment strategy by the determined shapes coordinate to be assigned into an area was introduced. The aim of this study is to gauge the capability of GA to solve this problem. Therefore some strategies to determine the chromosome representation and genetic operators are essential for less computational time and result quality. Some areas coordinate were used to generate the optimal solutions. The result indicates the GA is able to fulfill both feasible result and acceptable time.
Shape modification of Bézier curves by constrained optimization
Institute of Scientific and Technical Information of China (English)
WU Qing-biao; XIA Fei-hai
2005-01-01
The Bézier curve is one of the most commonly used parametric curves in CAGD and Computer Graphics and has many portant problem, and is also an important research issue in CAD/CAM and NC technology fields. This work investigates the curves to satisfy the given constraints and modify the shape of the curves optimally. Practical examples are also given.
Isogeometric Shape Optimization for Quasi-static and Transient Problems
Wang, Z.P.
2016-01-01
The recently developed isogeometric analysis (IGA) was aimed, from the start, at integrating computer aided design (CAD) and analysis. This synthesis of geometry and analysis has naturally led to renewed interest in developing structural shape optimization. The advantages of using isogeometric analy
Describing the Corneal Shape after Wavefront-Optimized Photorefractive Keratectomy
de Jong, Tim; Wijdh, Robert H. J.; Koopmans, Steven A.; Jansonius, Nomdo M.
2014-01-01
PURPOSE: To develop a procedure for describing wavefront-optimized photorefractive keratectomy (PRK) corneas and to characterize PRK-induced changes in shape. METHODS: We analyzed preoperative and postoperative corneal elevation data of 41 eyes of 41 patients (mean [±SD] age, 38 [±11] years) who und
Optimized comb drive finger shape for shock-resistant actuation
Engelen, Johan B.C.; Abelmann, Leon; Elwenspoek, Miko C.
2010-01-01
This work presents the analytical solution, realization and measurement of a comb drive with finger shapes optimized for shock-resistant actuation. The available force for actuating an external load determines how large shock forces can be compensated for. An analytical expression is presented for t
Combined shape and topology optimization of 3D structures
DEFF Research Database (Denmark)
Christiansen, Asger Nyman; Bærentzen, Jakob Andreas; Nobel-Jørgensen, Morten
2015-01-01
We present a method for automatic generation of 3D models based on shape and topology optimization. The optimization procedure, or model generation process, is initialized by a set of boundary conditions, an objective function, constraints and an initial structure. Using this input, the method...... will automatically deform and change the topology of the initial structure such that the objective function is optimized subject to the specified constraints and boundary conditions. For example, this tool can be used to improve the stiffness of a structure before printing, reduce the amount of material needed...
A free boundary approach to shape optimization problems.
Bucur, D; Velichkov, B
2015-09-13
The analysis of shape optimization problems involving the spectrum of the Laplace operator, such as isoperimetric inequalities, has known in recent years a series of interesting developments essentially as a consequence of the infusion of free boundary techniques. The main focus of this paper is to show how the analysis of a general shape optimization problem of spectral type can be reduced to the analysis of particular free boundary problems. In this survey article, we give an overview of some very recent technical tools, the so-called shape sub- and supersolutions, and show how to use them for the minimization of spectral functionals involving the eigenvalues of the Dirichlet Laplacian, under a volume constraint.
Isogeometric shape optimization of photonic crystals via Coons patches
DEFF Research Database (Denmark)
Qian, Xiaoping; Sigmund, Ole
2011-01-01
of multiple patches is motivated by the need for representing topologically complex geometries. The Coons patches are used as a design representation so that designers do not need to specify interior control points and they provide a mechanism to compute analytical sensitivities for internal nodes in shape...... in the parametric domain of the Coons patches with a built-in mesh rectifier to ensure the injectivity of the resulting B-spline geometry, i.e. every point in the physical domain is mapped to one point in the parametric domain, (3) analytical sensitivities. Sensitivities of objective functions and constraints......In this paper, we present an approach that extends isogeometric shape optimization from optimization of rectangular-like NURBS patches to the optimization of topologically complex geometries. We have successfully applied this approach in designing photonic crystals where complex geometries have...
Estimation of Radio Interferometer Beam Shapes Using Riemannian Optimization
Yatawatta, Sarod
2012-01-01
The knowledge of receiver beam shapes is essential for accurate radio interferometric imaging. Traditionally, this information is obtained by holographic techniques or by numerical simulation. However, such methods are not feasible for an observation with time varying beams, such as the beams produced by a phased array radio interferometer. We propose the use of the observed data itself for the estimation of the beam shapes. We use the directional gains obtained along multiple sources across the sky for the construction of a time varying beam model. The construction of this model is an ill posed non linear optimization problem. Therefore, we propose to use Riemannian optimization, where we consider the constraints imposed as a manifold. We compare the performance of the proposed approach with traditional unconstrained optimization and give results to show the superiority of the proposed approach.
Iso-geometric shape optimization of magnetic density separators
DEFF Research Database (Denmark)
Dang Manh, Nguyen; Evgrafov, Anton; Gravesen, Jens;
2014-01-01
Purpose The waste recycling industry increasingly relies on magnetic density separators. These devices generate an upward magnetic force in ferro-fluids allowing to separate the immersed particles according to their mass density. Recently, a new separator design has been proposed that significantly...... covers with B-splines and defines a cost functional that measures the non-uniformity of the magnetic field in an area above the poles. The authors apply an iso-geometric shape optimization procedure, which allows us to accurately represent, analyze and optimize the geometry using only a few design...... variables. The design problem is regularized by imposing constraints that enforce the convexity of the pole cover shapes and is solved by a non-linear optimization procedure. The paper validates the implementation of the algorithm using a simplified variant of the design problem with a known analytical...
Sareni, Bruno; Krähenbühl, Laurent; Muller, Daniel
1998-01-01
In this paper, we present a new approach for automatic design of electrodes. The investigated method consists in identifying an optimal shape from an optimal equipotential resulting from a system of point charges. The electric field and potential are computed using the point charge simulation method. Niching genetic algorithms and constrained optimization techniques are applied to the electrode benchmark in order to find multiple optimal profiles.
Notch stress and shape optimization; Kerbspannung und Kerbformoptimierung
Energy Technology Data Exchange (ETDEWEB)
Scherrer, M.
2004-08-01
The scientific field of biomechanics deals with the statics and dynamics of biological load carriers and the transfer of biological optimization strategies to technical applications. By observations of biological load carriers in nature a fundamental design rule could be developed called the axiom of uniform stress, which basically says that in temporal average with a certain load, there are neither high local stresses nor underloaded areas in a biological load carrier. Through load-controlled growth the load carrier gets material in areas with high stress as in areas with low stress there is no growth and hence no material. From this a shape optimization is obtained which is able to prevent fatigue failure. The adaptive growth of biological load carriers is simulated by the CAO-Method (computer aided optimization) and the FEM. With the help of the CAO-Method a parameter study for the optimization of shoulder fillets was made from which a geometrical characterisation of the optimized fillet shapes was derived. From that new ways for shape optimization were developed which offer design rules using alternative fillet shapes and a better understanding of the effects caused by stress concentrations was obtained. Due to this knowledge a new and efficient optimization method was developed which offers a fast and simple way to construct optimized fillet shapes. This method can be expressed analytically and was verified with several examples. (orig.) [German] Die Biomechanik befasst sich mit der Statik und Dynamik von biologischen Lasttraegern und der Uebertragung biologischer Optimierungsstrategien in die Technik. Aus Beobachtungen am Objekt in der Natur ging als eine grundlegende Designregel das Axiom der konstanten Spannung hervor, welches besagt, dass bei einem biologischen Lasttraeger bei bestimmungsgemaesser Belastung im zeitlichen Mittel weder lokal hohe Spannungen noch unterbelastete Bereiche auftreten. Der biologische Lasttraeger lagert durch lastgesteuertes
Institute of Scientific and Technical Information of China (English)
金鑫; 孙刚
2012-01-01
Aerodynamic drag reduction design is the key to the design of civil aircraft. To solve the drag reduction problem of wing a new method was proposed based on non-uniform B-spline modeling technology and an improved particle swarm optimization(PSO) algorithm. The former was used to describe the wing shapes with small amount of calculation: it not only had good local control of shape, but also ensured the overall appearance of smoothness; the latter, as a new intelligent optimization method, had fast convergence ability and global search ability for multi-objective optimization problems. The results showed that cubic non-uniform B-spline curves and bi-cubic non-uniform B-spline surface could describe the airfoil and wing shapes more accurately with fewer control points, and the efficiency of multi-objective aerodynamic optimization had been improved. Even for the airfoil and wing with high efficiency factor, aerodynamic performance also made a further increase.%机翼减阻设计是民用客机气动设计的关键,本文提出了一种基于非均匀B样条曲线曲面造型技术和改进的粒子群算法的新型优化方法.前者用来描述机翼的外形,具有计算量小的优点,在优化过程中不仅具有良好的局部操控性,又能保证整体外形的光顺性；后者作为一种新兴的智能化优化方法,具有简单易行、收敛速度快、全局搜索能力强等优点,同时又适用于多目标优化问题.研究结果表明:三次非均匀B样条曲线曲面能够方便地使用较少的控制顶点较为精确地描述翼型及机翼的外形,在此基础上利用改进的粒子群算法进行的多目标气动优化设计,优化效率得到了提升.在效率因子本身较高的初始外形基础上,最终外形的气动性能也取得了较大幅度的提高.
Optimization of bow shape for a non ballast water ship
Van He, Ngo; Ikeda, Yoshiho
2013-09-01
In this research, a commercial CFD code "Fluent" was applied to optimization of bulbous bow shape for a non ballast water ships (NBS). The ship was developed at the Laboratory of the authors in Osaka Prefecture University, Japan. At first, accuracy of the CFD code was validated by comparing the CFD results with experimental results at towing tank of Osaka Prefecture University. In the optimizing process, the resistances acting on ships in calm water and in regular head waves were defined as the object function. Following features of bulbous bow shapes were considered as design parameters: volume of bulbous bow, height of its volume center, angle of bow bottom, and length of bulbous bow. When referring to the computed results given by the CFD like resistance, pressure and wave pattern made by ships in calm water and in waves, an optimal bow shape for ships was discovered by comparing the results in the series of bow shapes. In the computation on waves, the ship is in fully captured condition because shorter waves, λ/ L pp <0.6, are assumed.
Optimization of endwall contouring in axial compressor S-shaped ducts
Directory of Open Access Journals (Sweden)
Jin Donghai
2015-08-01
Full Text Available This paper presents a numerical investigation of the potential aerodynamic benefits of using endwall contouring in a fairly aggressive duct with six struts based on the platform for endwall design optimization. The platform is constructed by integrating adaptive genetic algorithm (AGA, design of experiments (DOE, response surface methodology (RSM based on the artificial neural network (ANN, and a 3D Navier–Stokes solver. The visual analysis method based on DOE is used to define the design space and analyze the impact of the design parameters on the target function (response. Optimization of the axisymmetric and the non-axisymmetric endwall contouring in an S-shaped duct is performed and evaluated to minimize the total pressure loss. The optimal ducts are found to reduce the hub corner separation and suppress the migration of the low momentum fluid. The non-axisymmetric endwall contouring is shown to remove the separation completely and reduce the net duct loss by 32.7%.
A multiobjective shape optimization study for a subsonic submerged inlet
Taskinoglu, Ezgi S.
The purpose of the present work is to summarize the findings of a multiobjective shape optimization study conducted for a subsonic submerged air vehicle inlet. The objective functions of the optimization problem are distortion and swirl indices defined by the distribution of flow parameters over the exit cross-section of the inlet. The geometry alteration is performed by placing a protrusion in the shape of a fin on the baseline inlet surface. Thus, the design variables of the optimization problem are chosen to be the geometrical parameters defining the fin protrusion; namely fin height, length and incidence angle. The Trade Off (also known as epsilon-constraint) method is employed for finding the Pareto optimal set formed by the nondominated solutions of the feasible design space. Since the flow domain solution is required for every step along the line search, an automated optimization loop is constructed by integrating the optimizer with a surface modeler, a mesh generator and a flow solver through which the flow parameters over the compressor face are computed. In addition, the trade study for fin protrusion, the analyses and the comparison of the baseline and Pareto optimal solutions are presented and observations concerning grid resolution and convergence behaviour are discussed. The results display an irregular and discontinuous Pareto optimal set. Optimum inlet designs are scattered in two regions from which one representative inlet design is chosen and analyzed. As a result, it is concluded that an inlet designer has two options within the framework of this optimization study: an inlet design with high swirl but low distortion or an inlet design with low swirl but higher distortion.
Shape Optimization Of Front Axle Support Of Tractor
Directory of Open Access Journals (Sweden)
Shree Dewangan
2014-04-01
Full Text Available The front axle support of tractor is the part of tractor which holds the engine of tractor and also gives support to it and lies between engine and front axle of tractor. According to the present market demand of off highway vehicle the low cost and light weight vehicle is in demand to fulfill the requirement of cost efficient vehicle. In this paper analysis of front axle support is done for study of stress generated in the component and then after optimization of its shape and according to the shape its weight will also reduced. Considering the effect of forces acted on such a heavy parts in tractor designed by casting having dynamic loads of less frequency with greater amplitude may cause great damage to the component. According to the production techniques of components in tractor front axle requires a properly designed support with high stiffness. The design of component was modeled in Creo parametric 2.0 and the analysis was performed in solid works. Shape optimization technique is used for performing optimization cause miserable reduction in weight of connecting rod. The optimized component is 10.35% lighter compare to initial design.
Optimization on shape curves with application to specular stereo
Balzer, Jonathan
2010-01-01
We state that a one-dimensional manifold of shapes in 3-space can be modeled by a level set function. Finding a minimizer of an independent functional among all points on such a shape curve has interesting applications in computer vision. It is shown how to replace the commonly encountered practice of gradient projection by a projection onto the curve itself. The outcome is an algorithm for constrained optimization, which, as we demonstrate theoretically and numerically, provides some important benefits in stereo reconstruction of specular surfaces. © 2010 Springer-Verlag.
Fin shape thermal optimization using Bejan's constuctal theory
Lorenzini, Giulio
2011-01-01
The book contains research results obtained by applying Bejan's Constructal Theory to the study and therefore the optimization of fins, focusing on T-shaped and Y-shaped ones. Heat transfer from finned surfaces is an example of combined heat transfer natural or forced convection on the external parts of the fin, and conducting along the fin. Fin's heat exchange is rather complex, because of variation of both temperature along the fin and convective heat transfer coefficient. Furthermore possible presence of more fins invested by the same fluid flow has to be considered.Classical fin theory tri
Baecher, Juergen; Bandte, Oliver; DeLaurentis, Dan; Lewis, Kemper; Sicilia, Jose; Soboleski, Craig
1995-01-01
This report documents the efforts of a Georgia Tech High Speed Civil Transport (HSCT) aerospace student design team in completing a design methodology demonstration under NASA's Advanced Design Program (ADP). Aerodynamic and propulsion analyses are integrated into the synthesis code FLOPS in order to improve its prediction accuracy. Executing the integrated product and process development (IPPD) methodology proposed at the Aerospace Systems Design Laboratory (ASDL), an improved sizing process is described followed by a combined aero-propulsion optimization, where the objective function, average yield per revenue passenger mile ($/RPM), is constrained by flight stability, noise, approach speed, and field length restrictions. Primary goals include successful demonstration of the application of the response surface methodolgy (RSM) to parameter design, introduction to higher fidelity disciplinary analysis than normally feasible at the conceptual and early preliminary level, and investigations of relationships between aerodynamic and propulsion design parameters and their effect on the objective function, $/RPM. A unique approach to aircraft synthesis is developed in which statistical methods, specifically design of experiments and the RSM, are used to more efficiently search the design space for optimum configurations. In particular, two uses of these techniques are demonstrated. First, response model equations are formed which represent complex analysis in the form of a regression polynomial. Next, a second regression equation is constructed, not for modeling purposes, but instead for the purpose of optimization at the system level. Such an optimization problem with the given tools normally would be difficult due to the need for hard connections between the various complex codes involved. The statistical methodology presents an alternative and is demonstrated via an example of aerodynamic modeling and planform optimization for a HSCT.
Dynamic Characteristics of Electrostatically Actuated Shape Optimized Variable Geometry Microbeam
Directory of Open Access Journals (Sweden)
Sha Zhang
2015-01-01
Full Text Available We mainly analyze the dynamic characteristics of electrostatically actuated shape optimized variable geometry microbeam. A nonlinear dynamic model considering midplane stretching, electrostatic force, and electrical field fringing effects is developed. Firstly, we study the static responses of the optimized microbeams under DC polarization voltage. The generalized differential quadrature method (GDQM is used. Secondly, the dynamic responses of the shape optimized microbeams driven by DC and AC voltages are investigated using GDQM in conjunction with Levenberg-Marquardt optimization method. The results show that the more gradual change in width, the larger the resonant frequency and the maximum amplitude at resonance. Then we further discuss in detail how do the maximum width, midsection width, and curvature of the width function affect the frequency response of the microbeams. We find that the amplitude and resonant frequency of the dynamic response are not monotonically increasing as the curvature of the width function increases and there exists a critical curvature. This analysis will be helpful in the optimal design of MEMS actuators. Finally, for more consideration, different residual stress, squeeze-film damping, and fringing effect models are introduced into the governing equation of motion and we compare the corresponding dynamic response.
Shaping both Light & Material for Optimal Light‐Matter Interaction
DEFF Research Database (Denmark)
Glückstad, Jesper
on these scales involves the combination of optimal light‐sculpting [4] with the use of optimized shapes in micro‐ and nano‐robotic structures [5]. Micro‐fabrication processes such as two‐photon photo‐polymerization offer three‐dimensional resolutions for crafting custom‐designed monolithic microstructures...... that can be equipped with optical trapping handles for convenient opto‐mechanical control using only optical forces. Such microstructures ‐ as illustrated above ‐ can be effectively handled with simultaneous top‐ and side‐view on our proprietary BioPhotonics Workstation (BWS) to undertake six...
Flow simulation and shape optimization for aircraft design
Kroll, Norbert; Gauger, Nicolas R.; Brezillon, Joel; Dwight, Richard; Fazzolari, Antonio; Vollmer, Daniel; Becker, Klaus; Barnewitz, Holger; Schulz, Volker; Hazra, Subhendu
2007-06-01
Within the framework of the German aerospace research program, the CFD project MEGADESIGN was initiated. The main goal of the project is the development of efficient numerical methods for shape design and optimization. In order to meet the requirements of industrial implementations a co-operative effort has been set up which involves the German aircraft industry, the DLR, several universities and some small enterprises specialized in numerical optimization. This paper outlines the planned activities within MEGADESIGN, the status at the beginning of the project and it presents some early results achieved in the project.
Optimal boundary conditions at the staircase-shaped coastlines
Kazantsev, Eugene
2014-01-01
A 4D-Var data assimilation technique is applied to the rectangular-box configuration of the NEMO in order to identify the optimal parametrization of boundary conditions at lateral boundaries. The case of the staircase-shaped coastlines is studied by rotating the model grid around the center of the box. It is shown that, in some cases, the formulation of the boundary conditions at the exact boundary leads to appearance of exponentially growing modes while optimal boundary conditions allow to correct the errors induced by the staircase-like appriximation of the coastline.
Geometric constraints for shape and topology optimization in architectural design
Dapogny, Charles; Faure, Alexis; Michailidis, Georgios; Allaire, Grégoire; Couvelas, Agnes; Estevez, Rafael
2017-02-01
This work proposes a shape and topology optimization framework oriented towards conceptual architectural design. A particular emphasis is put on the possibility for the user to interfere on the optimization process by supplying information about his personal taste. More precisely, we formulate three novel constraints on the geometry of shapes; while the first two are mainly related to aesthetics, the third one may also be used to handle several fabrication issues that are of special interest in the device of civil structures. The common mathematical ingredient to all three models is the signed distance function to a domain, and its sensitivity analysis with respect to perturbations of this domain; in the present work, this material is extended to the case where the ambient space is equipped with an anisotropic metric tensor. Numerical examples are discussed in two and three space dimensions.
Sonic boom focusing prediction and delta wing shape optimization for boom mitigation studies
Khasdeo, Nitin
nose angle and dihedral angle on mitigating the sonic-boom ground signature. Optimal shape design for low sonic boom ground signature and least degradation of aerodynamic performance are the main goals of the present work. Response surface methodology is used for carrying out wing shape optimization. Far-field computations are carried out to predict the sonic boom signature on the ground using the full-potential code and the Thomas ray code.
Irregular Shaped Building Design Optimization with Building Information Modelling
Directory of Open Access Journals (Sweden)
Lee Xia Sheng
2016-01-01
Full Text Available This research is to recognise the function of Building Information Modelling (BIM in design optimization for irregular shaped buildings. The study focuses on a conceptual irregular shaped “twisted” building design similar to some existing sculpture-like architectures. Form and function are the two most important aspects of new buildings, which are becoming more sophisticated as parts of equally sophisticated “systems” that we are living in. Nowadays, it is common to have irregular shaped or sculpture-like buildings which are very different when compared to regular buildings. Construction industry stakeholders are facing stiff challenges in many aspects such as buildability, cost effectiveness, delivery time and facility management when dealing with irregular shaped building projects. Building Information Modelling (BIM is being utilized to enable architects, engineers and constructors to gain improved visualization for irregular shaped buildings; this has a purpose of identifying critical issues before initiating physical construction work. In this study, three variations of design options differing in rotating angle: 30 degrees, 60 degrees and 90 degrees are created to conduct quantifiable comparisons. Discussions are focused on three major aspects including structural planning, usable building space, and structural constructability. This research concludes that Building Information Modelling is instrumental in facilitating design optimization for irregular shaped building. In the process of comparing different design variations, instead of just giving “yes or no” type of response, stakeholders can now easily visualize, evaluate and decide to achieve the right balance based on their own criteria. Therefore, construction project stakeholders are empowered with superior evaluation and decision making capability.
Optimal shape of entrances for a frictionless nanochannel
Belin, Christophe; Joly, Laurent; Detcheverry, François
2016-09-01
The nearly frictionless flow of water in narrow carbon nanotubes is a genuine nanofluidic phenomenon with many prospects of applications in membrane technology. When inner dissipation is vanishing, the limiting factor to high flux lies in the viscous dissipation occurring at the tube mouth. As shown by Gravelle et al. [Gravelle, Joly, Detcheverry, Ybert, Cottin-Bizonne, and Bocquet, Proc. Natl. Acad. Sci. USA 110, 16367 (2013), 10.1073/pnas.1306447110], these so-called end effects can be reduced by adding a conical entrance. In this work, we take a step further and search for the optimal entrance shape. We use finite element calculations to compute the hydrodynamic resistance of a frictionless tube with superellipse-shaped entrances and propose an approximate analytical model. If perfect slip applies on its wall, an optimal entrance which is only 10 tube radii in length is sufficient to reduce end effects by an order of magnitude, a performance almost three times better than the optimal cone. In the case of partial slip, the resistance decreases with the entrance length before reaching a plateau at an optimal length controlled by liquid-solid slip. Our results are discussed in connection with biological and artificial systems.
Shape optimization of a thick-walled power boiler component
Directory of Open Access Journals (Sweden)
Duda Piotr
2017-01-01
Full Text Available This paper presents a methodology and successful application of structural optimization of a T-pipe under transient thermal and mechanical loads. In order to find the optimal shape of a thick-walled power boiler component, a parametric FE model and the evolutionary algorithm (EA are applied. The power boiler start-up and shutdown curves are based on the TRD 301 guidelines. Maximum total stresses are assumed as optimization constraints. The obtained geometry is by about 18.6% lighter than the original one due to thinning of the walls. Maximum tensile and compressive stresses in the modified geometry are smaller than in the original one during the whole cycle. Additionally, lower total stress values are recorded during heating and cooling processes. Therefore, these transient processes can be accelerated and the shutdown and start-up losses can be reduced.
Aerodynamic Optimization of Vertical Axis Wind Turbine with Trailing Edge Flaps
DEFF Research Database (Denmark)
Ertem, Sercan; Ferreira, Carlos; Gaunaa, Mac;
2016-01-01
Vertical Axis Wind Turbines (VAWT) are competitive concepts for very large scale (1020 MW) floating offshore applications. Rotor circulation control (loading control) opens a wide design space to enhance the aerodynamic and operational features of VAWT. The modified linear derivation...... on a real VAWT rotor to enhance its capabilities....
In-Space Radiator Shape Optimization using Genetic Algorithms
Hull, Patrick V.; Kittredge, Ken; Tinker, Michael; SanSoucie, Michael
2006-01-01
Future space exploration missions will require the development of more advanced in-space radiators. These radiators should be highly efficient and lightweight, deployable heat rejection systems. Typical radiators for in-space heat mitigation commonly comprise a substantial portion of the total vehicle mass. A small mass savings of even 5-10% can greatly improve vehicle performance. The objective of this paper is to present the development of detailed tools for the analysis and design of in-space radiators using evolutionary computation techniques. The optimality criterion is defined as a two-dimensional radiator with a shape demonstrating the smallest mass for the greatest overall heat transfer, thus the end result is a set of highly functional radiator designs. This cross-disciplinary work combines topology optimization and thermal analysis design by means of a genetic algorithm The proposed design tool consists of the following steps; design parameterization based on the exterior boundary of the radiator, objective function definition (mass minimization and heat loss maximization), objective function evaluation via finite element analysis (thermal radiation analysis) and optimization based on evolutionary algorithms. The radiator design problem is defined as follows: the input force is a driving temperature and the output reaction is heat loss. Appropriate modeling of the space environment is added to capture its effect on the radiator. The design parameters chosen for this radiator shape optimization problem fall into two classes, variable height along the width of the radiator and a spline curve defining the -material boundary of the radiator. The implementation of multiple design parameter schemes allows the user to have more confidence in the radiator optimization tool upon demonstration of convergence between the two design parameter schemes. This tool easily allows the user to manipulate the driving temperature regions thus permitting detailed design of in
Simultaneous beam sampling and aperture shape optimization for SPORT
Energy Technology Data Exchange (ETDEWEB)
Zarepisheh, Masoud; Li, Ruijiang; Xing, Lei, E-mail: Lei@stanford.edu [Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States); Ye, Yinyu [Department of Management Science and Engineering, Stanford University, Stanford, California 94305 (United States)
2015-02-15
Purpose: Station parameter optimized radiation therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital linear accelerators, in which the station parameters of a delivery system, such as aperture shape and weight, couch position/angle, gantry/collimator angle, can be optimized simultaneously. SPORT promises to deliver remarkable radiation dose distributions in an efficient manner, yet there exists no optimization algorithm for its implementation. The purpose of this work is to develop an algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: The authors build a mathematical model with the fundamental station point parameters as the decision variables. To solve the resulting large-scale optimization problem, the authors devise an effective algorithm by integrating three advanced optimization techniques: column generation, subgradient method, and pattern search. Column generation adds the most beneficial stations sequentially until the plan quality improvement saturates and provides a good starting point for the subsequent optimization. It also adds the new stations during the algorithm if beneficial. For each update resulted from column generation, the subgradient method improves the selected stations locally by reshaping the apertures and updating the beam angles toward a descent subgradient direction. The algorithm continues to improve the selected stations locally and globally by a pattern search algorithm to explore the part of search space not reachable by the subgradient method. By combining these three techniques together, all plausible combinations of station parameters are searched efficiently to yield the optimal solution. Results: A SPORT optimization framework with seamlessly integration of three complementary algorithms, column generation, subgradient method, and pattern search, was established. The proposed technique was applied to two previously treated clinical cases: a head and
Variable-complexity aerodynamic optimization of an HSCT wing using structural wing-weight equations
Hutchison, M. G.; Unger, E. R.; Mason, W. H.; Grossman, B.; Haftka, R. T.
1992-01-01
A new approach for combining conceptual and preliminary design techniques for wing optimization is presented for the high-speed civil transport (HSCT). A wing-shape parametrization procedure is developed which allows the linking of planform and airfoil design variables. Variable-complexity design strategies are used to combine conceptual and preliminary-design approaches, both to preserve interdisciplinary design influences and to reduce computational expense. In the study, conceptual-design-level algebraic equations are used to estimate aircraft weight, supersonic wave drag, friction drag and drag due to lift. The drag due to lift and wave drag are also evaluated using more detailed, preliminary-design-level techniques. The methodology is applied to the minimization of the gross weight of an HSCT that flies at Mach 3.0 with a range of 6500 miles.
CST气动外形参数化方法研究%A Study on CST Aerodynamic Shape Parameterization Method
Institute of Scientific and Technical Information of China (English)
关晓辉; 李占科; 宋笔锋
2012-01-01
类别形状函数变换(CST)方法是通过类别函数和形状函数来表示几何外形的新型气动外形参数化方法.通过考察参数化过程线性系统的条件数以及对翼型的表示误差,研究了Bernstein多项式阶数(BPO)对CST方法单值性和精度的影响,并将CST方法与B样条法、Hicks-Henne法和参数化翼型(PARSEC)法的参数数量和表示精度进行了对比.使用基于CST参数化方法的远场组元(FCE)激波阻力优化方法对超声速机翼进行外形优化,优化后的机翼其激波阻力降低达61％.研究结果表明:CST方法具有参数少,精度高的优点；为保证表示精度,同时避免病态参数化过程,应使用4阶以上、10阶以下的Bernstein多项式定义形状函数.%Class-shape-transformation (CST) Is a new shape parameterization method which represents the geometries of aircraft shapes with a class function and a shape function. Based on the condition numbers of linear systems and the representation residuals in the parameterization process, a study is performed on the influence of the bernstein polynomial order (BPO) on the numerical uniqueness and the precision of the CST method. Comparisons of parameter number and representation precision between the CST method and B-spline, Hicks-Henne and parametric section( PARSEC) methods are represented in this paper, as well as a supersonic wing shape optimization case using the far-field composite-element (FCE) wave drag optimization method which yields a 61 % reduction of wave drag. It is suggested that the CST parameterization Is characterized by high precision and low parameter number. In order to achieve sufficient precision and avoid ill-conditioned parameterization, the shape function should be defined by bernstein polynomials of at least 4th order, but no more than 10th order.
Multiobjective muffler shape optimization with hybrid acoustics modeling.
Airaksinen, Tuomas; Heikkola, Erkki
2011-09-01
This paper considers the combined use of a hybrid numerical method for the modeling of acoustic mufflers and a genetic algorithm for multiobjective optimization. The hybrid numerical method provides accurate modeling of sound propagation in uniform waveguides with non-uniform obstructions. It is based on coupling a wave based modal solution in the uniform sections of the waveguide to a finite element solution in the non-uniform component. Finite element method provides flexible modeling of complicated geometries, varying material parameters, and boundary conditions, while the wave based solution leads to accurate treatment of non-reflecting boundaries and straightforward computation of the transmission loss (TL) of the muffler. The goal of optimization is to maximize TL at multiple frequency ranges simultaneously by adjusting chosen shape parameters of the muffler. This task is formulated as a multiobjective optimization problem with the objectives depending on the solution of the simulation model. NSGA-II genetic algorithm is used for solving the multiobjective optimization problem. Genetic algorithms can be easily combined with different simulation methods, and they are not sensitive to the smoothness properties of the objective functions. Numerical experiments demonstrate the accuracy and feasibility of the model-based optimization method in muffler design.
Blade Shape Optimization of Liquid Turbine Flow Sensor
Institute of Scientific and Technical Information of China (English)
郭素娜; 张涛; 孙立军; 杨振; 杨文量
2016-01-01
Based on the characteristic curve analysis, the method using 2D(K ) square difference of meter factor at different flow rates was developed to evaluate the performance of turbine flow sensor in this study. Then according to the distribution of entrance velocity, it was supposed that reducing the blade area near the tip could decrease the linearity error of a sensor. Therefore, the influence of different blade shape parameters on the performance of the sensor was investigated by combining computational fluid dynamics(CFD)simulation with experimental test. The experimental results showed that, for the liquid turbine flow sensor with a diameter of 10 mm, the linearity error was smallest, and the performance of sensor was optimal when blade shape parameter equaled 0.25.
Isogeometric Analysis and Shape Optimization in Fluid Mechanics
DEFF Research Database (Denmark)
Nielsen, Peter Nørtoft
approximations, and for shape optimization purposes also due to its tight connection between the analysis and geometry models. The thesis is initiated by short introductions to fluid mechanics, and to the building blocks of isogeometric analysis. As the first contribution of the thesis, a detailed description...... is given of how isogeometric analysis is applied to flow problems. We present several new discretizations of the velocity and pressure spaces, we investigate these in terms of stability and error convergence properties, and a benchmark flow problem is analyzed. As the second contribution, we show how...
高效气动优化设计方法%Efficient Aerodynamic Design Optimization of Complex Configuration
Institute of Scientific and Technical Information of China (English)
傅林; 左英桃
2012-01-01
基于CFD方法开展气动外形优化设计通常计算量较大,采用离散共轭方法计算目标函数梯度,建立了高效的飞机气动优化设计系统.采用NURBS方法对翼剖面几何外形的扰动量进行参数化,避免了对原始外形的拟合,建立了基于NURBS方法的机翼剖面参数化方法.在复杂外形的优化设计中,动网格方法是关键技术之一,采用无限插值方法生成变形后的网格,并提出采用无限插值方法处理部件之间相贯线发生变化的情况.最后开展了翼身组合体+吊舱+挂架等复杂外形的优化设计,成功地减小了阻力,证明了方法的有效性.%Large scales of computations are required in aerodynamic optimization based on CFD methodologies.Efficient aerodynamic design optimization system is built in this paper,and the gradients of object functions are calculated with discrete adjoint method.The geometric perturbations of wing sections are parameterized with NURBS method,furthermore parameterization methodology of wing based on NURBS are built.Moving grid is one of key technologies in aerodynamic optimization design of very complex configuration.Transfinite interpolation methodology is utilized to generate new grid, and a methodology based on transfinite interpolation technology is proposed to deal with the surface grid in the case of junction lines varying.Configurations including wing - body - nacelle - pylon are optimized with the design optimization system.The drag is reduced successfully, which illustrates the effectiveness of the methodology built in this paper.
Shape Optimization of Inclined Ribs as Heat Transfer Augmentation Device
Institute of Scientific and Technical Information of China (English)
Kwang-Yong Kim; Hong-Min Kim
2006-01-01
This work presents numerical optimization techniques for the design of a rectangular channel with inclined ribs to enhance turbulent heat transfer.The response surface method with Reynolds-averaged Navier-Stokes analysis is used for optimization.Shear stress transport turbulence model is used as a turbulence closure.Computational results for local heat transfer rate show a reasonable agreement with the experimental data.Width-to-rib height ratio and attack angle of the rib are chosen as design variables.The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with the weighting factor.Full-factorial experimental design method is used to determine the data points.Optimum shapes of the channel have been obtained in a range of the weighting factor.
Theory and numerics for shape optimization in superconductivity
Energy Technology Data Exchange (ETDEWEB)
Heese, H.
2006-07-21
We consider a mathematical model for a thin superconducting film which is magnetically shielded by permanent magnets in order to improve the current carrying capability of the film. In a first part we study the behaviour of the magnetic field of the combined system, which is characterized via a boundary value problem for Laplace's equation for the quasi-scalar magnetic potential. In a second part we formulate and analyze a related geometric optimization problem that can be interpreted as a homogenization of the current distribution in the superconducting film by means of shape optimization for the magnet boundaries. We present a uniqueness and existence analysis for the boundary value problem based on boundary integral equations. The theoretical studies are complemented by a numerical approximation scheme for the potential, for which we prove exponential convergence rates under appropriate smoothness assumptions on the geometry. As central result for the geometric optimization problem we prove the differentiable dependence of the current distribution on the geometry, which also leads to an abstract existence result. Based on the differentiability result we derive two numerical schemes to realize the geometric optimization problem iteratively. The first approach relies on explicit parametrizations for the boundaries leading to a steepest descent scheme. The second approach uses level set methods which are based on an implicit boundary representation. The feasibility of both approaches is shown in a variety of examples. (orig.)
Performance Trades Study for Robust Airfoil Shape Optimization
Li, Wu; Padula, Sharon
2003-01-01
From time to time, existing aircraft need to be redesigned for new missions with modified operating conditions such as required lift or cruise speed. This research is motivated by the needs of conceptual and preliminary design teams for smooth airfoil shapes that are similar to the baseline design but have improved drag performance over a range of flight conditions. The proposed modified profile optimization method (MPOM) modifies a large number of design variables to search for nonintuitive performance improvements, while avoiding off-design performance degradation. Given a good initial design, the MPOM generates fairly smooth airfoils that are better than the baseline without making drastic shape changes. Moreover, the MPOM allows users to gain valuable information by exploring performance trades over various design conditions. Four simulation cases of airfoil optimization in transonic viscous ow are included to demonstrate the usefulness of the MPOM as a performance trades study tool. Simulation results are obtained by solving fully turbulent Navier-Stokes equations and the corresponding discrete adjoint equations using an unstructured grid computational fluid dynamics code FUN2D.
Aerodynamic Optimization of Vertical Axis Wind Turbine with Trailing Edge Flap
DEFF Research Database (Denmark)
Ertem, Sercan; Ferreira, Carlos Simao; Gaunaa, Mac;
2016-01-01
Vertical Axis Wind Turbines (VAWT) are competitive concepts for very large scale (10-20 MW)floating ofshore applications. Rotor circulation control (loading control) opens a wide design space to enhance the aerodynamic and operational features of VAWT. The modied linear derivation of the Actuator...... gains for various solidity, tip-speed ratio, maximum ap defection and ap size are quantifed in inviscidow. This extensive work presents new insights on the performance of a VAWT with innite number of blades as well as it provides a solid foundation forap usage on a real VAWT rotor to enhance its...
Optimization and experimental verification for aerodynamic scheme of flying-wing%飞翼布局气动方案优选和试验验证
Institute of Scientific and Technical Information of China (English)
鲍君波; 王钢林; 武哲
2012-01-01
The characteristic arguments to describe the plane shape considering the stealthy and aerody- namic performance of the flying-wing was proposed, the constraint relation in the scheme optimization was ana- lyzed. The 3-dimensional curved surface model was built by using parameterization method, and the process to divide the surface grids was packaged automatically. The new surface grids can be generated accurately and rapidly by changing the design arguments, thus the iteration efficiency in the scheme optimization process was improved. The aerodynamic performance was calculated by using the numerical method based on the Euler e- quation, the viscous correction was added in the analysis of the major scheme. The stealthy performance was estimated by using the high-frequency approximate method. The cruise status was taken as the design point to optimize the aerodynamic scheme considering the constraints of stealthy performance based on analysis-modifi- cation method, and the selected scheme was tested by the wind tunnel. The results prove the research deserv- ing the selected scheme.%提出综合考虑飞翼布局隐身性能和气动性能的平面形状特征参数，分析了方案优选中的约束关系，采用参数化方法构建了三维曲面模型，并将物面网格划分流程进行自动化封装，通过更改设计参数准确快速地得到新方案的物面网格，应用基于Euler方程的数值方法进行布局方案的气动性能计算分析，在重点方案的分析中加入黏性修正；应用高频近似方法估算方案的隐身性能．以巡航状态作为设计点，在隐身性能的约束下，应用分析一修正的方法完成了气动布局方案优选，并对最终选定的方案进行风洞试验验证，证明该方案有进一步研究的价值。
Shape optimization for low Neumann and Steklov eigenvalues
Girouard, Alexandre
2008-01-01
We give an overview of results on shape optimization for low eigenvalues of the Laplacian on bounded planar domains with Neumann and Steklov boundary conditions. These results share a common feature: they are proved using methods of complex analysis. In particular, we present modernized proofs of the classical inequalities due to Szego and Weinstock for the first nonzero Neumann and Steklov eigenvalues. We also extend the inequality for the second nonzero Neumann eigenvalue, obtained recently by Nadirashvili and the authors, to non-homogeneous membranes with log-subharmonic densities. In the homogeneous case, we show that this inequality is strict, which implies that the maximum of the second nonzero Neumann eigenvalue is not attained in the class of simply-connected membranes of a given mass. The same is true for the second nonzero Steklov eigenvalue, as follows from our results on the Hersch-Payne-Schiffer inequalities.
Optimal Embedding for Shape Indexing in Medical Image Databases
Qian, Xiaoning; Tagare, Hemant D.; Fulbright, Robert K.; Long, Rodney; Antani, Sameer
2010-01-01
This paper addresses the problem of indexing shapes in medical image databases. Shapes of organs are often indicative of disease, making shape similarity queries important in medical image databases. Mathematically, shapes with landmarks belong to shape spaces which are curved manifolds with a well defined metric. The challenge in shape indexing is to index data in such curved spaces. One natural indexing scheme is to use metric trees, but metric trees are prone to inefficiency. This paper pr...
Optimal shape profiles for cooling fins of high and low conductivity
Energy Technology Data Exchange (ETDEWEB)
Bobaru, Florin; Rachakonda, Srinivas [Nebraska Univ., Dept. of Engineering Mechanics, Lincoln, NE (United States)
2004-11-01
We present a numerical approach able to capture the dependence of the optimal shape profiles of thermal fins on the conductivity parameters. We consider the two-dimensional cross-section of a periodic array of fins and involve the third dimension via the thermal boundary layer. The highly conductive fins converge to 'sharp-pointed', narrow base shapes while the low conductivity ones prefer blunted, wide base fins. The optimal shapes we obtain are similar to the shapes of intestinal villi and stegosaurus plates. A meshfree method, coupled with a gradient-based optimization algorithm, is used to handle the significant shape changes from a simple, generic initial guess to the final, optimal shape. We reach the optimal shapes without remeshing. (Author)
Institute of Scientific and Technical Information of China (English)
李珺; 杨永; 顾祥玉
2014-01-01
在飞行器概念－初步设计阶段，建立基于C FD的气动优化链对于提高优化计算的效率具有较好的工程应用价值。使用德国宇航院开发的CPACS数据格式给出飞行器平面形状，结合NURBS翼型参数化方法对飞行器几何外形进行参数化；自动生成计算网格并求解Euler方程数值模拟流场以评估参数化气动外形的气动特性，进而构建响应面模型；使用SQP梯度算法搜索响应面模型以获取满足约束的最优解。以Onera M6机翼为例，对该优化链进行验证。结果表明：在满足约束的条件下，基于C FD的气动优化链能够成功地进行气动外形优化。%An aerodynamic optimization chain based on CFD is of great significance for conceptual and prelimina‐ry design .The combination of NURBS(Non‐Uniform Rational B‐Splines) parameterization method and CPACS (Common Parametric Aircraft Configuration Schema) data format developed by Deutsches Zentrum für Luft‐und Raumfahrt(DLR) can successfully describe the parameterized configuration of the entire aircraft .The grids for calculating the Euler equations are automatically generated and the aerodynamic characteristics of parameterized aerodynamic shape are evaluated .Then the response surface model(RSM ) is built .Based on RSM the SQP(Se‐quential Quadratic Programming) gradient algorithm is sought under satisfying constraints .An Onera M6 wing is chosen to validate the optimization chain .The optimization results indicate that under conditions of constraint ,aerody‐namic configuration can be optimized successfully by an aerodynamic optimization chain based on CFD .
Institute of Scientific and Technical Information of China (English)
廖炎平; 刘莉; 龙腾
2011-01-01
Forward- Swept wing (FSW) configuration provides a now direction for the aerodynamic configuration desigu of UAV benause its excellent aerodynamic characteristics. The Class-Shape function Transformation (CST) method is used to describe the parameterized airfoil geometry. The parameterized models for aerodynamic and stealthy performance of FSW are constructed. The aerodynamic analysis model of FSW is constructed by computational fluid dynamics method basod on N - S equations. Tbe stealthy performance analysis model of FSW is constructed by computational electromagnetics method based Method of Moments ( MoM ). The multi - objective aerodynamic and stealthy performance optimization method for FSW using Kriging model is presented. The Latin hypercube method is employed to get a set of sample points. The aerodynamic and stealthy perfomance Kriging models are built. The multi-objective aerodynamic and stealthy performance optimization of FSW is optimized by combining Pareto genetic algorithm with Krigthg model. The results of the investigation show that the constructed analysis models are reasonable and the presented multi- objective optimization design method is feasible ,which can improve the performance of large- aspect- ratio FSW and the efficiency of optimization effiectively.%前掠翼布局优越的气动性能为无人机气动布局设计提供了一条新的方向.采用CST方法对翼型几何外形进行参数化描述,实现前掠翼气动和隐身多学科优化设计模型的参数化描述.建立了基于N-S方程的计算流体力学方法的前掠翼气动分析模型和基于矩量法的计算电磁学方法的前掠翼隐身分析模型.提出了基于Kriging模型的前掠翼气动隐身多目标优化方法,采用拉丁超方试验设计方法获取样本点,建立前掠翼气动和隐身的Kriging代理模型.将Pareto多目标遗传算法与Kriging代理模型结合进行大展弦比前掠翼的气动隐身多目标优化设计.研究结果表
Riebe, John M; Naeseth, Rodger L
1953-01-01
An investigation was made in the Langley 300 mph 7-by 10-foot tunnel to determine the aerodynamic characteristics of a refined deep-step planing-tail hull with various forebody and afterbody shapes. For comparison, tests were made on a streamline body simulating the fuselage of a modern transport airplane. The results of the tests, which include the interference effects of a 21-percent-thick support wing, indicated that for corresponding configurations the hull models incorporating a forebody with a length-beam ratio of 7 had lower minimum drag coefficients than the hull models incorporating a forebody with a length-beam ratio of 5. Longitudinal and lateral stability was generally about the same for all hull models tested and about the same as that of a conventional hull.
Institute of Scientific and Technical Information of China (English)
许波峰; 王同光; 张震宇; 王珑
2013-01-01
风力机叶片采用分裂式叶尖小翼可以改善叶片的气动性能.以风能利用系数最大和风轮推力系数最小为目标,采用自由涡尾迹(FVW)方法与快速非支配排序遗传算法(NSGA-Ⅱ)耦合对小翼的形状进行优化设计.NS-GA-Ⅱ算法对每一代种群进行评价、筛选和变异,最终得到小翼形状的Pareto最优解集,其中气动性能评价目标通过FVW方法计算.结果表明,FVW模型能够较准确的模拟叶片的气动性能；两目标优化给出的不是传统优化方法追求的单个最优解,而是一个Pareto最优解集,且分布在一条曲线上；相比NREL原始叶片,风能利用系数最高能提高30％；小翼的几何形状在最优解集下分布具有一定的规律性,对后面的设计及改型有很好的指导性作用.%Forked winglet can improve the aerodynamic performance of wind turbine blades.Taking the maximum power coefficient and the minimum thrust coefficient as the optimization objectives, couple the free vortex wake (FVW) method and the fast and elitist non-dominated sorting genetic algorithm (NSGA-Ⅱ) to optimize the winglet shape.NSGA- Ⅱ can obtain the Pareto-optimal solutions of winglet shape by evaluating, selecting and mutating the population members, of this aerodynamic performance is calculated by FVW method.The results indicate that FVW method could simulate the aerodynamic performance accurately, and two objectives optimization gives a Pareto-optimal solution set distributing on a curve rather than the particular optimum solution.Power coefficient can be increased by 30 percent than original NREL blade.The distribution of winglet geometry has some regularity which can guide the later works of design and modification.
Optimization of a New Aerodynamic Cylindrical FAIMS Device for Small Molecule Analysis
Purves, Randy W.; Prasad, Satendra; Belford, Michael; Vandenberg, Albert; Dunyach, Jean-Jacques
2017-03-01
The implementation of an aerodynamic mechanism to improve ion sampling between nanoelectrospray (n-ESI) and FAIMS was recently reported for proteomic analyses. This investigation explores the new FAIMS interface for small molecule analysis at high liquid flow rates and includes an examination of key differences in ionization between heated-ESI (HESI) and n-ESI. The sheath gas, critical for desolvation with HESI, affects FAIMS operation as higher FAIMS gas flow rates are required to achieve sufficient desolvation. Gas flow rate experiments also uncovered m/z discrimination with the conventional design as larger (slower moving) m/z ions experienced larger signal intensity losses than smaller m/z ions due to the desolvation gas flow having a greater drag effect on slower moving ions. The modified inlet in new FAIMS dampens the gas drag, making the HESI source more amenable as less m/z bias and significantly lower %RSD values were observed. Furthermore, a larger radius inner electrode in new FAIMS enables significantly higher E/N (electric field/number gas density) to be achieved using the existing waveform generator. Thus, new FAIMS signal intensities using only nitrogen improved 1.25- to 2-fold compared with the conventional design and 50% helium. Adding helium to the new FAIMS gave no significant improvements. The larger inner electrode also decreased ion focusing capabilities, and the effect on peak separation and ion intensity was examined in detail. The peak capacity of new FAIMS was approximately double that of conventional FAIMS; separation of seven low m/z ions gave a peak capacity of 37.7 using the gas additive 2-propanol.
Etzel, P. B.; Martin, R.; Romeo, R.; Fesen, R.; Hale, R.; Taghavi, R.; Anthony-Twarog, B. J.; Shawl, S. J.; Twarog, B. A.
2004-12-01
The focus of ULTRA (see poster by Twarog et al.) is a three-year plan to develop and test ultralightweight technology for research applications in astronomy. The goal is to demonstrate that a viable alternative exists to traditional glass-mirror technology by designing, fabricating, and testing a research telescope prototype comprising fiber reinforced plastic (CFRP) materials. To date, several mirror designs have been tested. The main goal in the first year has been to develop a 0.4m diameter mirror and OTA that serve as prototypes for the 1m telescope design. Mirrors of 0.4m diameter have been successfully fabricated which yield diffraction limited images. This poster will include a display of the complete OTA (including optics), optics test results, and astronomical images taken with prototype mirrors. Finite element analysis has been used to evaluate the OTA and mirror designs. Preliminary design details were incorporated in a knowledge-based system. Adaptive Modeling Language (AML), an object oriented programming language developed by Technosoft, Inc., was used to develop a parameterized geometric model of the preliminary design. The system can generate mirrors with radials/circumferentials, tube core substructures, as well as modeling the support structure. Computational fluid dynamics analyses were performed for sweep, inclination and ambient wind speed. Finite element analyses were performed for core density and arrangement, skin thickness, back-surface curvature, spider configuration and arrangement of the OTA, while the loading conditions considered thus far are thermal, inertial, and aerodynamic pressure loads. Experimental tests, including ultrasonic nondestructive evaluations, infrared imaging, modal testing, and wind tunnel tests, have been performed on the first prototype mirror, with the primary goal of validating analytical models and identifying potential manufacturing induced variations to be expected among "like" mirrors. Support of this work by
A LEVEL SET BASED SHAPE OPTIMIZATION METHOD FOR AN ELLIPTIC OBSTACLE PROBLEM
Burger, Martin
2011-04-01
In this paper, we construct a level set method for an elliptic obstacle problem, which can be reformulated as a shape optimization problem. We provide a detailed shape sensitivity analysis for this reformulation and a stability result for the shape Hessian at the optimal shape. Using the shape sensitivities, we construct a geometric gradient flow, which can be realized in the context of level set methods. We prove the convergence of the gradient flow to an optimal shape and provide a complete analysis of the level set method in terms of viscosity solutions. To our knowledge this is the first complete analysis of a level set method for a nonlocal shape optimization problem. Finally, we discuss the implementation of the methods and illustrate its behavior through several computational experiments. © 2011 World Scientific Publishing Company.
Institute of Scientific and Technical Information of China (English)
PENG Peng; YANG Quan
2009-01-01
Load distribution is the foundation of shape control and gauge control, in which it is necessary to take into account the shape control ability of TCM (tandem cold mill) for strip shape and gauge quality. First, the objective function of generalized shape and gauge decoupling load distribution optimization was established, which considered the rolling force characteristics of the first and last stands in TCM, the relative power, and the TCM shape control ability. Then, IGA (immune genetic algorithm) was used to accomplish this multi-objective load distribution optimization for TCM. After simulation and comparison with the practical load distribution strategy in one tandem cold mill, general-ized shape and gauge decoupling load distribution optimization on the basis of IGA approved good ability of optimizing shape control and gauge control simultaneously.
Sensitivity Analysis Based Multiple Objective Preform Die Shape Optimal Design in Metal Forging
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The multiple objective preform design optimization was put forward. The final forging's shape and deformation uniformity were considered in the multiple objective. The objective is to optimize the shape and the deformation uniformity of the final forging at the same time so that a more high integrate quality of the final forging can be obtained. The total objective was assembled by the shape and uniformity objective using the weight adding method. The preform die shape is presented by cubic B-spline curves. The control points of B-spline curves are used as the design variables. The forms of the total objective function, shape and uniformity sub-objective function are given. The sensitivities of the total objective function and the sub-objective functions with respect to the design variables are developed. Using this method, the preform die shape of an H-shaped forging process is optimally designed. The optimization results are very satisfactory.
Shape optimization of road tunnel cross-section by simulated annealing
Directory of Open Access Journals (Sweden)
Sobótka Maciej
2016-06-01
Full Text Available The paper concerns shape optimization of a tunnel excavation cross-section. The study incorporates optimization procedure of the simulated annealing (SA. The form of a cost function derives from the energetic optimality condition, formulated in the authors’ previous papers. The utilized algorithm takes advantage of the optimization procedure already published by the authors. Unlike other approaches presented in literature, the one introduced in this paper takes into consideration a practical requirement of preserving fixed clearance gauge. Itasca Flac software is utilized in numerical examples. The optimal excavation shapes are determined for five different in situ stress ratios. This factor significantly affects the optimal topology of excavation. The resulting shapes are elongated in the direction of a principal stress greater value. Moreover, the obtained optimal shapes have smooth contours circumscribing the gauge.
Bryson, Christopher; Hussain, Fazle; Barhorst, Alan
2015-11-01
Optimization of wind turbine torque as a function of angle of attack - over the entire speed range from start-up to cut-off - is studied by considering the full trigonometric relations projecting lift and drag to thrust and torque. Since driving force and thrust are geometrically constrained, one cannot be changed without affecting the other. Increasing lift to enhance torque simultaneously increases thrust, which subsequently reduces the inflow angle with respect to the rotor plane via an increased reduction in inflow velocity. Reducing the inflow angle redirects the lift force away from the driving force generating the torque, which may reduce overall torque. Similarly, changes in the tip-speed ratio (TSR) affect the inflow angle and thus the optimal torque. Using the airfoil data from the NREL 5 MW reference turbine, the optimal angle of attack over the operational TSR range (4 to 15) was computed using a BEM model to incorporate the dynamic coupling, namely the interdependency of blade loading and inflow angle. The optimal angle of attack is close to minimum drag during start-up phase (high TSR) and continuously increases toward maximum lift at high wind speeds (low TSR).
Doubrawa, P.; Barthelmie, R. J.; Wang, H.; Churchfield, M. J.
2016-09-01
The contribution of wake meandering and shape asymmetry to load and power estimates is quantified by comparing aeroelastic simulations initialized with different inflow conditions: an axisymmetric base wake, an unsteady stochastic shape wake, and a large-eddy simulation with rotating actuator-line turbine representation. Time series of blade-root and tower base bending moments are analyzed. We find that meandering has a large contribution to the fluctuation of the loads. Moreover, considering the wake edge intermittence via the stochastic shape model improves the simulation of load and power fluctuations and of the fatigue damage equivalent loads. These results indicate that the stochastic shape wake simulator is a valuable addition to simplified wake models when seeking to obtain higher-fidelity computationally inexpensive predictions of loads and power.
Institute of Scientific and Technical Information of China (English)
雷鸣
2015-01-01
预警机在未来战场上所面对目标的 RCS 越来越小，为了获得足够的作用距离，需要增加雷达的功率口径积，在载机功率资源一定的情况下，增大天线口径是最有效的方法。然而机载预警雷达天线口径受雷达罩外形尺寸及飞机总体气动构型等因素的限制，因此需要合理选择预警机总体气动构型并对雷达罩气动外形进行优化；通过合理的结构总体布局设计，有效利用雷达罩的气动外形，保证天线口径的最大化，文中就雷达罩气动外形选择以及雷达结构总体设计的相关问题进行探讨，可为预警机雷达结构总体设计提供参考。%The RCS of target faced by the early warning aircraft is getting smaller and smaller.It is re-quired to augment the power-aperture product for gaining the adequate detection range.It is the most effica-cious way to enlarge the antenna aperture when the power provided by the aircraft is limited.However,the antenna aperture of AEW radar is limited by the outline of the radome as well as the overall aerodynamic con-figuration of the aircraft.On the one hand,it is demanded to choose the overall aerodynamic configuration of the aircraft reasonably and to optimize the outline of the radome and make an effective use.On the other hand,it is demanded to design the overall layout of the equipment of antenna system precisely,so as to ensure the antenna aperture indexes.The related issues about the aerodynamic shape choice of radome and the overall structral design of AEW radar are discussed.
Iron Pole Shape Optimization of IPM Motors Using an Integrated Method
Directory of Open Access Journals (Sweden)
JABBARI, A.
2010-02-01
Full Text Available An iron pole shape optimization method to reduce cogging torque in Interior Permanent Magnet (IPM motors is developed by using the reduced basis technique coupled by finite element and design of experiments methods. Objective function is defined as the minimum cogging torque. The experimental design of Taguchi method is used to build the approximation model and to perform optimization. This method is demonstrated on the rotor pole shape optimization of a 4-poles/24-slots IPM motor.
变体平尾翼型气动外形设计方法%Airfoil Aerodynamic Optimization Method of Morphing Horizontal Stabilizer
Institute of Scientific and Technical Information of China (English)
杜厦; 昂海松
2012-01-01
A morphing airfoil instead of traditional horizontal stabilizer and control elements is proposed in order to make the aircraft keep the optimal lift/drag ratio during flight attitude controlling. Bornstein polynomial with order "n" is used to describe the airfoil configuration. A set of airfoil that can provide a minimum drag coefficient at different lift coefficient in a confirmed flight environment is obtained by aerodynamic optimization simulation using the genetic algorithm. It is proved that the morphing airfoil can provide a smaller drag coefficient than the traditional control element do when the same lift coefficient is provided. The relationship between shape control parameters and lift is fitted according to the optimized airfoil. A set of example is used to verify the morphing regularity.%为了使飞机在控制飞行姿态时仍然能保持最优升阻比,提出了一种通过改变翼型形状来代替传统控制舵面采控制飞机俯仰的方法.采用伯恩斯坦多项式对机翼的翼型进行数学建模,并采用遗传算法通过空气动力学仿真对翼型进行优化得到一组在一定飞行环境下、产生附加阻力最小且随升力系数变化的翼型形状.通过对比证明在提供相同升力的情况下,变体翼比传统的控制舵面产生更小的附加阻力.根据翼型形状和升力系数的变化采用数据拟合的方法得到翼型形状控制参数随升力变化的规律.通过算例对变化规律的验证表明其可以用来作为飞行姿态控制的翼型形状变化依据.
Shape Optimization and Modular Discretization for the Development of a Morphing Wingtip
Morley, Joshua
Better knowledge in the areas of aerodynamics and optimization has allowed designers to develop efficient wingtip structures in recent years. However, the requirements faced by wingtip devices can be considerably different amongst an aircraft's flight regimes. Traditional static wingtip devices are then a compromise between conflicting requirements, resulting in less than optimal performance within each regime. Alternatively, a morphing wingtip can reconfigure leading to improved performance over a range of dissimilar flight conditions. Developed within this thesis, is a modular morphing wingtip concept that centers on the use of variable geometry truss mechanisms to permit morphing. A conceptual design framework is established to aid in the development of the concept. The framework uses a metaheuristic optimization procedure to determine optimal continuous wingtip configurations. The configurations are then discretized for the modular concept. The functionality of the framework is demonstrated through a design study on a hypothetical wing/winglet within the thesis.
Topology optimization of pulse shaping filters using the Hilbert transform envelope extraction
DEFF Research Database (Denmark)
Lazarov, Boyan Stefanov; Matzen, René; Elesin, Yuriy
2011-01-01
Time domain topology optimization is applied to design pulse shaping filters. The objective function depends on the pulse envelope, which is extracted by utilizing the Hilbert transform. The gradients with respect to the topology optimization variables are derived, and the optimization methodology...
Vasilyev, Oleg V.; Gazzola, Mattia; Koumoutsakos, Petros
2009-11-01
In this talk we discuss preliminary results for the use of hybrid wavelet collocation - Brinkman penalization approach for shape and topology optimization of fluid flows. Adaptive wavelet collocation method tackles the problem of efficiently resolving a fluid flow on a dynamically adaptive computational grid in complex geometries (where grid resolution varies both in space and time time), while Brinkman volume penalization allows easy variation of flow geometry without using body-fitted meshes by simply changing the shape of the penalization region. The use of Brinkman volume penalization approach allow seamless transition from shape to topology optimization by combining it with level set approach and increasing the size of the optimization space. The approach is demonstrated for shape optimization of a variety of fluid flows by optimizing single cost function (time averaged Drag coefficient) using covariance matrix adaptation (CMA) evolutionary algorithm.
Shape optimization of active and passive drag-reducing devices on a D-shaped bluff body
Semaan, Richard
2016-01-01
Shape optimization of an active and a passive drag-reducing device on a two-dimensional D-shaped bluff body is performed. The two devices are: Coanda actuator, and randomly-shaped trailing-edge flap. The optimization sequence is performed by coupling the genetic algorithm software DAKOTA to the mesh generator Pointwise and to the CFD solver OpenFOAM. For the the active device the cost functional is the power ratio, whereas for the passive device it is the drag coefficient. The optimization leads to total power savings of $\\approx 70\\%$ for the optimal Coanda actuator, and a 40\\% drag reduction for the optimal flap. This reduction is mainly achieved through streamlining the base flow and suppressing the vortex shedding. The addition of either an active or a passive device creates two additional smaller recirculation regions in the base cavity that shifts the larger recirculation region away from the body and increases the base pressure. The results are validated against more refined URANS simulations for selec...
Shape optimization of a Sodium Fast Reactor core
Directory of Open Access Journals (Sweden)
Dombre Emmanuel
2013-01-01
Full Text Available We apply in this paper a geometrical shape optimization method for the design of the core of a SFR (Sodium-cooled Fast Reactor in order to minimize a thermal counter-reaction known as the sodium void effect. In this kind of reactors, by increasing the temperature, the core may become liable to a strong increase of reactivity, a key-parameter governing the chain-reaction at quasi-static states. We first use the one group energy diffusion model and give the generalization to the two groups energy equation. We then give some numerical results in the case of the one group energy equation. Note that the application of our method leads to some designs whose interfaces can be parametrized by very smooth curves which can stand very far from realistic designs. We don’t explain here the method that it would be possible to use for recovering an operational design but there exists several penalization methods (see [2] that could be employed to this end. On applique dans cet article une méthode d’optimisation géométrique dans le cadre de la conception d’un cœur de réacteur SFR (Sodium-cooled Fast Reactor, i.e. réacteur à neutron rapide refroidi au sodium dans le but de minimiser une contre réaction thermique connue sous le nom d’effet de vidange sodium. Lorsqu’une augmentation de température survient, ce type de réacteur peut être sujet à une forte augmentation de réactivité, un paramètre clé dans le contrôle de la réaction en chaîne en régime quasi-statique. On a recours à l’équation de diffusion à un groupe puis on donne la généralisation du modèle d’optimisation pour l’équation de la diffusion à deux groupes d’énergie. On présente ensuite quelques résultats numériques obtenus dans le cas de l’équation à un groupe d’énergie. On note que l’application de cette méthode conduit à des designs de cœur présentant des interfaces très régulières qui sont loin d’un design de cœur faisable sur le
Institute of Scientific and Technical Information of China (English)
Min LIU; Keqi WU
2008-01-01
Based on the immersed boundary method (IBM) and the finite volume optimized pre-factored compact (FVOPC) scheme, a numerical simulation of noise propagation inside and outside the casing of a cross flow fan is estab-lished. The unsteady linearized Euler equations are solved to directly simulate the aero-acoustic field. In order to validate the FVOPC scheme, a simulation case: one dimensional linear wave propagation problem is carried out using FVOPC scheme, DRP scheme and HOC scheme. The result of FVOPC is in good agreement with the ana-lytic solution and it is better than the results of DRP and HOC schemes, the FVOPC is less dispersion and dissi-pation than DRP and HOC schemes. Then, numerical simulation of noise propagation problems is performed. The noise field of 36 compact rotating noise sources is obtained with the rotating velocity of 1000r/min. The PML absorbing boundary condition is applied to the sound far field boundary condition for depressing the numerical reflection. Wall boundary condition is applied to the casing. The results show that there are reflections on the casing wall and sound wave interference in the field. The FVOPC with the IBM is suitable for noise propagation problems under the complex geometries for depressing the dispersion and dissipation, and also keeping the high order precision.
Optimizing the Esthetics of peg-shaped teeth
Directory of Open Access Journals (Sweden)
Fabia Danielle Sales da Cunha Medeiros e Silva
2008-01-01
Full Text Available In modern esthetic dentistry, recontouring peg-shaped teeth present the option of a technique for obtaining a harmonious smile. In thiscontext, the advancement of direct dental materials, such as resin composites and adhesive systems, allows this procedure to be performedsimply and efficiently, when compared with other available techniques. Thus, the aim of this report is to present a clinical case with an esthetic solution in peg-shaped lateral incisors (12 and 22. Initially, it was opted first to perform dental bleaching with a home bleaching gel (16% carbamide peroxide associated with an acetate mold duly made for this purpose. The peg-shaped teeth were recontoured with a microhybrid resin composite (shade EA1 and DA1 with the aid of a platinum guide in silicone, obtained after diagnostic waxing on the plaster model. It was concluded that the association of esthetic procedures is of the utmost importance for obtaining good looking, aligned and harmonious teeth.
Baelmans, M.; Blommaert, M.; Dekeyser, W.; Van Oevelen, T.
2017-03-01
Plasma edge transport codes play a key role in the design of future divertor concepts. Their long simulation times in combination with a large number of control parameters turn the design into a challenging task. In aerodynamics and structural mechanics, adjoint-based optimization techniques have proven successful to tackle similar design challenges. This paper provides an overview of achievements and remaining challenges with these techniques for complex divertor design. It is shown how these developments pave the way for fast sensitivity analysis and improved design from different perspectives.
Novel free-form hohlraum shape design and optimization for laser-driven inertial confinement fusion
Energy Technology Data Exchange (ETDEWEB)
Jiang, Shaoen; Jing, Longfei, E-mail: scmyking-2008@163.com; Ding, Yongkun [Laser Fusion Research Center, China Academy Engineering Physics, Mianyang 621900 (China); Huang, Yunbao, E-mail: huangyblhy@gmail.com [Mechatronics School of Guangdong University of Technology, Guangzhou 510006 (China)
2014-10-15
The hohlraum shape attracts considerable attention because there is no successful ignition method for laser-driven inertial confinement fusion at the National Ignition Facility. The available hohlraums are typically designed with simple conic curves, including ellipses, parabolas, arcs, or Lame curves, which allow only a few design parameters for the shape optimization, making it difficult to improve the performance, e.g., the energy coupling efficiency or radiation drive symmetry. A novel free-form hohlraum design and optimization approach based on the non-uniform rational basis spline (NURBS) model is proposed. In the present study, (1) all kinds of hohlraum shapes can be uniformly represented using NURBS, which is greatly beneficial for obtaining the optimal available hohlraum shapes, and (2) such free-form uniform representation enables us to obtain an optimal shape over a large design domain for the hohlraum with a more uniform radiation and higher drive temperature of the fuel capsule. Finally, a hohlraum is optimized and evaluated with respect to the drive temperature and symmetry at the Shenguang III laser facility in China. The drive temperature and symmetry results indicate that such a free-form representation is advantageous over available hohlraum shapes because it can substantially expand the shape design domain so as to obtain an optimal hohlraum with high performance.
多级离心风机的气动优化设计%Aerodynamic optimization design of multistage centrifugal fan
Institute of Scientific and Technical Information of China (English)
石硕; 张晓非; 张国成
2012-01-01
The optimization of fan plays an important role in energy saving and emission reduction of our industrial and mining enterprises. Based on the theory of aerodynamic performance calculation, in view of inadequate suction and poor efficiency of multistage centrifugal blower, the paper carries out aerodynamic optimization design. In the conditions of limiting the cost and volume of the fan, through the analysis of the structure and aerodynamic performance of the single stage, the paper analyzes the impact loss of impeller, equivalent conical angle, pre-rotation, resonance frequency and other factors. The aerodynamic re-count result shows that the pressure increases by 15. 3% when a blade is added to the impeller and the return-channel and the return-channel size is changed.%风机的优化改造,对我国工矿企业的节能减排有重大的意义.文章基于通风机气动计算基本理论,针对原多级离心风机吸力不足,效率较差的特点,对其进行优化设计.在制造成本,风机体积等改进限制条件下,通过研究单级的结构和气动性能,分析了叶轮进口气流损失、当量扩张角、预旋、频率共振等因素的影响.经气动复算,结果表明,对叶轮和回流器各增加一片叶片并改变回流器尺寸后,整机压力提高15.3％.
A Shape Optimization Study for Tool Design in Resistance Welding
DEFF Research Database (Denmark)
Bogomolny, Michael; Bendsøe, Martin P.; Hattel, Jesper Henri
2009-01-01
the objective is to prolong the life-time of the electrodes. Welding parameters like current, time and electrode shape parameters are selected to be the design variables while constraints are chosen to ensure a high quality of the welding. Surrogate models based on a Kriging approximation has been used in order...
Design of one-dimensional optical pulse-shaping filters by time-domain topology optimization
DEFF Research Database (Denmark)
Yang, Lirong; Lavrinenko, Andrei; Hvam, Jørn Märcher;
2009-01-01
Time-domain topology optimization is used here to design optical pulse-shaping filters in Si/SiO2 thin-film systems. A novel envelope objective function as well as explicit penalization are used to adapt the optimization method to this unique class of design problems.......Time-domain topology optimization is used here to design optical pulse-shaping filters in Si/SiO2 thin-film systems. A novel envelope objective function as well as explicit penalization are used to adapt the optimization method to this unique class of design problems....
Constellation Shaping for WDM systems using 256QAM/1024QAM with Probabilistic Optimization
DEFF Research Database (Denmark)
Yankov, Metodi Plamenov; Da Ros, Francesco; Porto da Silva, Edson;
2016-01-01
In this paper, probabilistic shaping is numerically and experimentallyinvestigated for increasing the transmission reach of wavelength divisionmultiplexed (WDM) optical communication system employing quadrature amplitudemodulation (QAM). An optimized probability mass function (PMF) of the QAMsymb...
Energy Technology Data Exchange (ETDEWEB)
Zarepisheh, M; Li, R; Xing, L [Stanford UniversitySchool of Medicine, Stanford, CA (United States); Ye, Y [Stanford Univ, Management Science and Engineering, Stanford, Ca (United States); Boyd, S [Stanford University, Electrical Engineering, Stanford, CA (United States)
2014-06-01
Purpose: Station Parameter Optimized Radiation Therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital LINACs, in which the station parameters of a delivery system, (such as aperture shape and weight, couch position/angle, gantry/collimator angle) are optimized altogether. SPORT promises to deliver unprecedented radiation dose distributions efficiently, yet there does not exist any optimization algorithm to implement it. The purpose of this work is to propose an optimization algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: We build a mathematical model whose variables are beam angles (including non-coplanar and/or even nonisocentric beams) and aperture shapes. To solve the resulting large scale optimization problem, we devise an exact, convergent and fast optimization algorithm by integrating three advanced optimization techniques named column generation, gradient method, and pattern search. Column generation is used to find a good set of aperture shapes as an initial solution by adding apertures sequentially. Then we apply the gradient method to iteratively improve the current solution by reshaping the aperture shapes and updating the beam angles toward the gradient. Algorithm continues by pattern search method to explore the part of the search space that cannot be reached by the gradient method. Results: The proposed technique is applied to a series of patient cases and significantly improves the plan quality. In a head-and-neck case, for example, the left parotid gland mean-dose, brainstem max-dose, spinal cord max-dose, and mandible mean-dose are reduced by 10%, 7%, 24% and 12% respectively, compared to the conventional VMAT plan while maintaining the same PTV coverage. Conclusion: Combined use of column generation, gradient search and pattern search algorithms provide an effective way to optimize simultaneously the large collection of station parameters and significantly improves
Optimization of ultrasonic array inspections using an efficient hybrid model and real crack shapes
Energy Technology Data Exchange (ETDEWEB)
Felice, Maria V., E-mail: maria.felice@bristol.ac.uk [Department of Mechanical Engineering, University of Bristol, Bristol, U.K. and NDE Laboratory, Rolls-Royce plc., Bristol (United Kingdom); Velichko, Alexander, E-mail: p.wilcox@bristol.ac.uk; Wilcox, Paul D., E-mail: p.wilcox@bristol.ac.uk [Department of Mechanical Engineering, University of Bristol, Bristol (United Kingdom); Barden, Tim; Dunhill, Tony [NDE Laboratory, Rolls-Royce plc., Bristol (United Kingdom)
2015-03-31
Models which simulate the interaction of ultrasound with cracks can be used to optimize ultrasonic array inspections, but this approach can be time-consuming. To overcome this issue an efficient hybrid model is implemented which includes a finite element method that requires only a single layer of elements around the crack shape. Scattering Matrices are used to capture the scattering behavior of the individual cracks and a discussion on the angular degrees of freedom of elastodynamic scatterers is included. Real crack shapes are obtained from X-ray Computed Tomography images of cracked parts and these shapes are inputted into the hybrid model. The effect of using real crack shapes instead of straight notch shapes is demonstrated. An array optimization methodology which incorporates the hybrid model, an approximate single-scattering relative noise model and the real crack shapes is then described.
Iso-geometric shape optimization of magnetic density separators
2014-01-01
PurposeThe waste recycling industry increasingly relies on magnetic density separators. These devices generate an upward magnetic force in ferro-fluids allowing to separate the immersed particles according to their mass density. Recently, a new separator design has been proposed that significantly reduces the required amount of permanent magnet material. The purpose of this paper is to alleviate the undesired end-effects in this design by altering the shape of the ferromagnetic covers of the ...
Co-Optimization of Blunt Body Shapes for Moving Vehicles
Brown, James L. (Inventor); Garcia, Joseph A (Inventor); Kinney, David J. (Inventor); Bowles, Jeffrey V (Inventor); Mansour, Nagi N (Inventor)
2014-01-01
A method and associated system for multi-disciplinary optimization of various parameters associated with a space vehicle that experiences aerocapture and atmospheric entry in a specified atmosphere. In one embodiment, simultaneous maximization of a ratio of landed payload to vehicle atmospheric entry mass, maximization of fluid flow distance before flow separation from vehicle, and minimization of heat transfer to the vehicle are performed with respect to vehicle surface geometric parameters, and aerostructure and aerothermal vehicle response for the vehicle moving along a specified trajectory. A Pareto Optimal set of superior performance parameters is identified.
Shape interior modeling and mass property optimization using ray-reps
DEFF Research Database (Denmark)
Wu, Jun; Kramer, Lou; Westermann, Rüdiger
2016-01-01
We present a novel method for the modeling and optimization of the material distribution inside 3D shapes, such that their 3D printed replicas satisfy prescribed constraints regarding mass properties. In particular, we introduce an extension of ray-representation to shape interior modeling...
Design optimization of shape memory alloy active structures using the R-phase transformation
Langelaar, M.; Van Keulen, F.
2007-01-01
This article illustrates the opportunities that combining computational modeling and systematic design optimization techniques offer to facilitate the design process of shape memory alloy (SMA) structures. Focus is on shape memory behavior due to the R-phase transformation in Ni-Ti, for which a dedi
Knowledge-Based Shape Optimization of Morphing Wing for More Efficient Aircraft
Alessandro De Gaspari; Sergio Ricci
2015-01-01
An optimization procedure for the shape design of morphing aircraft is presented. The process is coupled with a knowledge-based framework combining parametric geometry representation, multidisciplinary modelling, and genetic algorithm. The parameterization method exploits the implicit properties of the Bernstein polynomial least squares fitting to allow both local and global shape control. The framework is able to introduce morphing shape changes in a feasible way, taking into accoun...
Directory of Open Access Journals (Sweden)
Shen-yan Chen
2015-01-01
Full Text Available This paper presents an Improved Genetic Algorithm with Two-Level Approximation (IGATA to minimize truss weight by simultaneously optimizing size, shape, and topology variables. On the basis of a previously presented truss sizing/topology optimization method based on two-level approximation and genetic algorithm (GA, a new method for adding shape variables is presented, in which the nodal positions are corresponding to a set of coordinate lists. A uniform optimization model including size/shape/topology variables is established. First, a first-level approximate problem is constructed to transform the original implicit problem to an explicit problem. To solve this explicit problem which involves size/shape/topology variables, GA is used to optimize individuals which include discrete topology variables and shape variables. When calculating the fitness value of each member in the current generation, a second-level approximation method is used to optimize the continuous size variables. With the introduction of shape variables, the original optimization algorithm was improved in individual coding strategy as well as GA execution techniques. Meanwhile, the update strategy of the first-level approximation problem was also improved. The results of numerical examples show that the proposed method is effective in dealing with the three kinds of design variables simultaneously, and the required computational cost for structural analysis is quite small.
From the Cover: Shape insensitive optimal adhesion of nanoscale fibrillar structures
Gao, Huajian; Yao, Haimin
2004-05-01
Gecko and many insects have adopted nanoscale fibrillar structures on their feet as adhesion devices. Here, we consider adhesion between a single fiber and a substrate by van der Waals or electrostatic interactions. For a given contact area A, the theoretical pull-off force of the fiber is thA where th is the theoretical strength of adhesion. We show that it is possible to design an optimal shape of the tip of the fiber to achieve the theoretical pull-off force. However, such design tends to be unreliable at the macroscopic scale because the pull-off force is sensitive to small variations in the tip shape. We find that a robust design of shape-insensitive optimal adhesion becomes possible only when the diameter of the fiber is reduced to length scales on the order of 100 nm. In general, optimal adhesion could be achieved by a combination of size reduction and shape optimization. The smaller the size, the less important the shape. At large contact sizes, optimal adhesion could still be achieved if the shape can be manufactured to a sufficiently high precision. The robust design of optimal adhesion at nanoscale provides a plausible explanation for the convergent evolution of hairy attachment systems in biology.
Reliability-Based Shape Optimization using Stochastic Finite Element Methods
DEFF Research Database (Denmark)
Enevoldsen, Ib; Sørensen, John Dalsgaard; Sigurdsson, G.
1991-01-01
Application of first-order reliability methods FORM (see Madsen, Krenk & Lind [8)) in structural design problems has attracted growing interest in recent years, see e.g. Frangopol [4), Murotsu, Kishi, Okada, Yonezawa & Taguchi [9) and Sørensen [14). In probabilistically based optimal design...
Optimized shapes of magnetic arrays for drug targeting applications
Barnsley, Lester C.; Carugo, Dario; Stride, Eleanor
2016-06-01
Arrays of permanent magnet elements have been utilized as light-weight, inexpensive sources for applying external magnetic fields in magnetic drug targeting applications, but they are extremely limited in the range of depths over which they can apply useful magnetic forces. In this paper, designs for optimized magnet arrays are presented, which were generated using an optimization routine to maximize the magnetic force available from an arbitrary arrangement of magnetized elements, depending on a set of design parameters including the depth of targeting (up to 50 mm from the magnet) and direction of force required. A method for assembling arrays in practice is considered, quantifying the difficulty of assembly and suggesting a means for easing this difficulty without a significant compromise to the applied field or force. Finite element simulations of in vitro magnetic retention experiments were run to demonstrate the capability of a subset of arrays to retain magnetic microparticles against flow. The results suggest that, depending on the choice of array, a useful proportion of particles (more than 10% ) could be retained at flow velocities up to 100 mm s-1 or to depths as far as 50 mm from the magnet. Finally, the optimization routine was used to generate a design for a Halbach array optimized to deliver magnetic force to a depth of 50 mm inside the brain.
Directory of Open Access Journals (Sweden)
Andreea Koreanschi
2017-02-01
Full Text Available In this paper, an ‘in-house’ genetic algorithm is described and applied to an optimization problem for improving the aerodynamic performances of an aircraft wing tip through upper surface morphing. The algorithm’s performances were studied from the convergence point of view, in accordance with design conditions. The algorithm was compared to two other optimization methods, namely the artificial bee colony and a gradient method, for two optimization objectives, and the results of the optimizations with each of the three methods were plotted on response surfaces obtained with the Monte Carlo method, to show that they were situated in the global optimum region. The optimization results for 16 wind tunnel test cases and 2 objective functions were presented. The 16 cases used for the optimizations were included in the experimental test plan for the morphing wing-tip demonstrator, and the results obtained using the displacements given by the optimizations were evaluated.
Institute of Scientific and Technical Information of China (English)
王元元; 张彬乾; 郭兆电; 董强
2013-01-01
利用非均匀有理B样条(NURBS)基函数属性建立了任意空间的自由变形(FFD)参数化方法,进一步结合无限插值(TFI)变形网格技术、二阶振荡粒子群优化(PSO)算法以及计算流体力学(CFD)数值模拟技术,构建了通用的气动外形优化设计系统.采用该系统对C17运输机上翘后体进行气动优化设计,在满足后体最大宽度、高度以及上翘角不减小的情况下,巡航状态减阻2.6％,压差阻力减小19.8％.流态分析显示,优化后体阻力减小的主要原因是后体截面近圆度的增加以及近圆度沿机身轴线的变化量的减小使得后体周向逆压梯度减小所致.研究结果表明本文建立的基于FFD技术的气动优化设计系统对于大型运输机上翘后体的气动优化设计具有较好的实用性.%A free-form deformation parameterization (FFD) method is established based on non-uniform rational B-spline (NURBS) basis function.Furthermore,by coupling the transfinite interpolation (TFI) grid deformation technology and computational fluid dynamics (CFD) method with improved particle swarm optimization (PSO) arithmetic,a general aerodynamic optimization design system is constructed.Then,the aerodynamic optimization design system is applied to designing a large upswept afterbody of transport aircraft C17 on the restrictions of nondecreasing maximum structure height,width and upswept angle.The optimized afterbody decreases the total drag by 2.6％ and pressure drag by 19.8％ respectively.A comparison analysis of the aerodynamic shape and flow pattern reveals that the key factors for the optimized afterbody to decrease the pressure drag greatly are the increased near-roundness of the afterbody cross-section and decreased near-roundness change ratio along the fuselage axis.The two factors enable the adverse pressure gradient along the circumferential direction to become smaller,which can suspend aferbody separation and weaken afterbody vortex strength
Optimal segmentation of pupillometric images for estimating pupil shape parameters.
De Santis, A; Iacoviello, D
2006-12-01
The problem of determining the pupil morphological parameters from pupillometric data is considered. These characteristics are of great interest for non-invasive early diagnosis of the central nervous system response to environmental stimuli of different nature, in subjects suffering some typical diseases such as diabetes, Alzheimer disease, schizophrenia, drug and alcohol addiction. Pupil geometrical features such as diameter, area, centroid coordinates, are estimated by a procedure based on an image segmentation algorithm. It exploits the level set formulation of the variational problem related to the segmentation. A discrete set up of this problem that admits a unique optimal solution is proposed: an arbitrary initial curve is evolved towards the optimal segmentation boundary by a difference equation; therefore no numerical approximation schemes are needed, as required in the equivalent continuum formulation usually adopted in the relevant literature.
An a posteriori error estimator for shape optimization: application to EIT
Giacomini, M.; Pantz, O.; Trabelsi, K.
2015-11-01
In this paper we account for the numerical error introduced by the Finite Element approximation of the shape gradient to construct a guaranteed shape optimization method. We present a goal-oriented strategy inspired by the complementary energy principle to construct a constant-free, fully-computable a posteriori error estimator and to derive a certified upper bound of the error in the shape gradient. The resulting Adaptive Boundary Variation Algorithm (ABVA) is able to identify a genuine descent direction at each iteration and features a reliable stopping criterion for the optimization loop. Some preliminary numerical results for the inverse identification problem of Electrical Impedance Tomography are presented.
Suppression of vortex-shedding noise via derivative-free shape optimization
Marsden, Alison L.; Wang, Meng; Dennis, J. E.; Moin, Parviz
2004-10-01
In this Letter we describe the application of a derivative-free optimization technique, the surrogate management framework (SMF), for designing the shape of an airfoil trailing edge which minimizes the noise of vortex shedding. Constraints on lift and drag are enforced within SMF using a filter. Several optimal shapes have been identified for the case of laminar vortex shedding with reasonable computational cost using several shape parameters, and results show a significant reduction in acoustic power. Physical mechanisms for noise reduction are discussed.
An optimization approach for extracting and encoding consistent maps in a shape collection
Huang, Qi-Xing
2012-11-01
We introduce a novel approach for computing high quality point-topoint maps among a collection of related shapes. The proposed approach takes as input a sparse set of imperfect initial maps between pairs of shapes and builds a compact data structure which implicitly encodes an improved set of maps between all pairs of shapes. These maps align well with point correspondences selected from initial maps; they map neighboring points to neighboring points; and they provide cycle-consistency, so that map compositions along cycles approximate the identity map. The proposed approach is motivated by the fact that a complete set of maps between all pairs of shapes that admits nearly perfect cycleconsistency are highly redundant and can be represented by compositions of maps through a single base shape. In general, multiple base shapes are needed to adequately cover a diverse collection. Our algorithm sequentially extracts such a small collection of base shapes and creates correspondences from each of these base shapes to all other shapes. These correspondences are found by global optimization on candidate correspondences obtained by diffusing initial maps. These are then used to create a compact graphical data structure from which globally optimal cycle-consistent maps can be extracted using simple graph algorithms. Experimental results on benchmark datasets show that the proposed approach yields significantly better results than state-of-theart data-driven shape matching methods. © 2012 ACM.
Directory of Open Access Journals (Sweden)
GHOLAMIAN, A. S.
2009-06-01
Full Text Available In this paper, a magnet shape optimization method for reduction of cogging torque and torque ripple in Permanent Magnet (PM brushless DC motors is presented by using the reduced basis technique coupled by finite element and design of experiments methods. The primary objective of the method is to reduce the enormous number of design variables required to define the magnet shape. The reduced basis technique is a weighted combination of several basis shapes. The aim of the method is to find the best combination using the weights for each shape as the design variables. A multi-level design process is developed to find suitable basis shapes or trial shapes at each level that can be used in the reduced basis technique. Each level is treated as a separated optimization problem until the required objective is achieved. The experimental design of Taguchi method is used to build the approximation model and to perform optimization. This method is demonstrated on the magnet shape optimization of a 6-poles/18-slots PM BLDC motor.
Analytical optimal pulse shapes obtained with the aid of genetic algorithms
Guerrero, Rubén D.; Arango, Carlos A.; Reyes, Andrés
2015-09-01
We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function using genetic algorithms. As a first application of the methodology, we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions.
Analytical optimal pulse shapes obtained with the aid of genetic algorithms
Energy Technology Data Exchange (ETDEWEB)
Guerrero, Rubén D., E-mail: rdguerrerom@unal.edu.co [Department of Physics, Universidad Nacional de Colombia, Bogota (Colombia); Arango, Carlos A. [Department of Chemical Sciences, Universidad Icesi, Cali (Colombia); Reyes, Andrés [Department of Chemistry, Universidad Nacional de Colombia, Bogota (Colombia)
2015-09-28
We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function using genetic algorithms. As a first application of the methodology, we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions.
Optimal shapes and stresses of adherent cells on patterned substrates
Banerjee, Shiladitya; Marchetti, M Cristina
2013-01-01
We investigate a continuum mechanical model for an adherent cell on two dimensional adhesive micropatterned substrates. The cell is modeled as an isotropic and homogeneous elastic material subject to uniform internal contractile stresses. The build-up of tension from cortical actin bundles at the cell periphery is incorporated by introducing an energy cost for bending of the cell boundary, resulting to a resistance to changes in local curvature. Integrin-based adhesions are modeled as harmonic springs, that pin the cell to adhesive patches of a predefined geometry. Using Monte Carlo simulations and analytical techniques we investigate the competing effects of bulk contractility and cortical bending rigidity in regulating cell shapes on non-adherent regions. We show that the crossover from convex to concave cell edges is controlled by the interplay between contractile stresses and boundary bending rigidity. In particular, the cell boundary becomes concave beyond a critical value of the contractile stress that ...
Optimal wavy surface to suppress vortex shedding using second-order sensitivity to shape changes
Tammisola, Outi
2016-01-01
A method to find optimal 2nd-order perturbations is presented, and applied to find the optimal spanwise-wavy surface for suppression of cylinder wake instability. Second-order perturbations are required to capture the stabilizing effect of spanwise waviness, which is ignored by standard adjoint-based sensitivity analyses. Here, previous methods are extended so that (i) 2nd-order sensitivity is formulated for base flow changes satisfying linearised Navier-Stokes, and (ii) the resulting method is applicable to a 2D global instability problem. This makes it possible to formulate 2nd-order sensitivity to shape modifications. Using this formulation, we find the optimal shape to suppress the a cylinder wake instability. The optimal shape is then perturbed by random distributions in full 3D stability analysis to confirm that it is a local optimal at the given amplitude and wavelength. Furthermore, it is shown that none of the 10 random wavy shapes alone stabilize the wake flow at Re=50, while the optimal shape does....
Katz, Joseph
2006-01-01
Race car performance depends on elements such as the engine, tires, suspension, road, aerodynamics, and of course the driver. In recent years, however, vehicle aerodynamics gained increased attention, mainly due to the utilization of the negative lift (downforce) principle, yielding several important performance improvements. This review briefly explains the significance of the aerodynamic downforce and how it improves race car performance. After this short introduction various methods to generate downforce such as inverted wings, diffusers, and vortex generators are discussed. Due to the complex geometry of these vehicles, the aerodynamic interaction between the various body components is significant, resulting in vortex flows and lifting surface shapes unlike traditional airplane wings. Typical design tools such as wind tunnel testing, computational fluid dynamics, and track testing, and their relevance to race car development, are discussed as well. In spite of the tremendous progress of these design tools (due to better instrumentation, communication, and computational power), the fluid dynamic phenomenon is still highly nonlinear, and predicting the effect of a particular modification is not always trouble free. Several examples covering a wide range of vehicle shapes (e.g., from stock cars to open-wheel race cars) are presented to demonstrate this nonlinear nature of the flow field.
Optimization of Compton Source Performance through Electron Beam Shaping
Energy Technology Data Exchange (ETDEWEB)
Malyzhenkov, Alexander [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Yampolsky, Nikolai [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-09-26
We investigate a novel scheme for significantly increasing the brightness of x-ray light sources based on inverse Compton scattering (ICS) - scattering laser pulses off relativistic electron beams. The brightness of ICS sources is limited by the electron beam quality since electrons traveling at different angles, and/or having different energies, produce photons with different energies. Therefore, the spectral brightness of the source is defined by the 6d electron phase space shape and size, as well as laser beam parameters. The peak brightness of the ICS source can be maximized then if the electron phase space is transformed in a way so that all electrons scatter off the x-ray photons of same frequency in the same direction, arriving to the observer at the same time. We describe the x-ray photon beam quality through the Wigner function (6d photon phase space distribution) and derive it for the ICS source when the electron and laser rms matrices are arbitrary.
Optimization of compton source performance through electron beam shaping
Malyzhenkov, Alexander; Yampolsky, Nikolai
2017-03-01
We investigate a novel scheme for significantly increasing the brightness of x-ray light sources based on inverse Compton scattering (ICS) - scattering laser pulses off relativistic electron beams. The brightness of ICS sources is limited by the electron beam quality, since electrons traveling at different angles, and/or having different energies, produce photons with different energies. Therefore, the spectral brightness of the source is defined by the 6D electron phase space shape and size, as well as laser beam parameters. The peak brightness of the ICS source can be maximized, then, if the electron phase space is transformed in a way such that all electrons scatter off the x-ray photons of same frequency in the same direction, arriving to the observer at the same time. We describe the x-ray photon beam quality through the Wigner function (6D photon phase space distribution), and derive it for the ICS source when the electron and laser rms matrices are arbitrary.
Morimoto, Kenichi; Kinoshita, Hidenori; Suzuki, Yuji
2016-11-01
In the present study, an adjoint-based shape-optimization method has been developed for designing extended heat transfer surfaces in conjugate heat transfer problems. Here we specifically consider heat conduction-dominated solidification problem under different thermal boundary conditions: (i) the isothermal condition, and (ii) the conjugate condition with thermal coupling between the solidified liquid and the solid wall inside the domain bounded by the extended heat transfer surface. In the present shape-optimization scheme, extended heat transfer surfaces are successively refined in a local way based on the variational information of a cost functional with respect to the shape modification. In the computation of the developed scheme, a meshless method is employed for dealing with the complex boundary shape. For high-resolution analyses with boundary-fitted node arrangement, we have introduced a bubble-mesh method combined with a high-efficiency algorithm for searching neighboring bubbles within a cut-off distance. The present technique can be easily applied to convection problems including high Reynolds number flow. We demonstrate, for the isothermal boundary condition, that the present optimization leads to tree-like fin shapes, which achieve the temperature field with global similarity for different initial fin shapes. We will also show the computational results for the conjugate condition, which would regularize the present optimization due to the fin-efficiency effect.
Correction of linear-array lidar intensity data using an optimal beam shaping approach
Xu, Fan; Wang, Yuanqing; Yang, Xingyu; Zhang, Bingqing; Li, Fenfang
2016-08-01
The linear-array lidar has been recently developed and applied for its superiority of vertically non-scanning, large field of view, high sensitivity and high precision. The beam shaper is the key component for the linear-array detection. However, the traditional beam shaping approaches can hardly satisfy our requirement for obtaining unbiased and complete backscattered intensity data. The required beam distribution should roughly be oblate U-shaped rather than Gaussian or uniform. Thus, an optimal beam shaping approach is proposed in this paper. By employing a pair of conical lenses and a cylindrical lens behind the beam expander, the expanded Gaussian laser was shaped to a line-shaped beam whose intensity distribution is more consistent with the required distribution. To provide a better fit to the requirement, off-axis method is adopted. The design of the optimal beam shaping module is mathematically explained and the experimental verification of the module performance is also presented in this paper. The experimental results indicate that the optimal beam shaping approach can effectively correct the intensity image and provide ~30% gain of detection area over traditional approach, thus improving the imaging quality of linear-array lidar.
Shape optimization of plate with static and dynamic constraints via virtual laminated element
Institute of Scientific and Technical Information of China (English)
李芳; 徐兴; 凌道盛
2003-01-01
The virtual laminated element method (VLEM) can resolve structural shape optimization problems with a new method. According to the characteristics of VLEM , only some characterized layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary. One of the important features of this method is that it is not necessary to regenerate the FE(finite element) grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements. The thickness distribution in thin plate optimization problems in other studies before is of stepped shape. However, in this paper, a continuous thickness distribution can be obtained after optimization using VLEM, and is more reasonable. Furthermore, an approximate reanalysis method named ″behavior model technique″ can be used to reduce the amount of structural reanalysis. Some typical examples are offered to prove the effectiveness and practicality of the proposed method.
Shape optimization of plate with static and dynamic constraints via virtual laminated element.
Li, Fang; Xu, Xing; Ling, Dao-Sheng
2003-01-01
The virtual laminated element method (VLEM) can resolve structural shape optimization problems with a new method. According to the characteristics of VLEM, only some characterised layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary. One of the important features of this method is that it is not necessary to regenerate the FE(finite element) grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements. The thickness distribution in thin plate optimization problems in other studies before is of stepped shape. However, in this paper, a continuous thickness distribution can be obtained after optimization using VLEM, and is more reasonable. Furthermore, an approximate reanalysis method named "behavior model technique" can be used to reduce the amount of structural reanalysis. Some typical examples are offered to prove the effectiveness and practicality of the proposed method.
Directory of Open Access Journals (Sweden)
Georgios E. Stavroulakis
2013-10-01
Full Text Available This paper presents a numerical study on optimal voltages and optimal placement of piezoelectric actuators for shape control of beam structures. A finite element model, based on Timoshenko beam theory, is developed to characterize the behavior of the structure and the actuators. This model accounted for the electromechanical coupling in the entire beam structure, due to the fact that the piezoelectric layers are treated as constituent parts of the entire structural system. A hybrid scheme is presented based on great deluge and genetic algorithm. The hybrid algorithm is implemented to calculate the optimal locations and optimal values of voltages, applied to the piezoelectric actuators glued in the structure, which minimize the error between the achieved and the desired shape. Results from numerical simulations demonstrate the capabilities and efficiency of the developed optimization algorithm in both clamped−free and clamped−clamped beam problems are presented.
Shape Design of Lifting body Based on Genetic Algorithm
Directory of Open Access Journals (Sweden)
Yongyuan Li
2010-11-01
Full Text Available This paper briefly introduces the concept and history of lifting body, and puts forward a new method for the optimization of lifting body. This method has drawn lessons from the die line design of airplane is used to parametric numerical modeling for the lifting body, and extract the characterization of shape parameters as design variables, a combination of lifting body reentry vehicle aerodynamic conditions, aerodynamic heating, volumetric Rate and the stability of performance. Multi-objective hybrid genetic algorithm is adopted to complete the aerodynamic shape optimization and design of hypersonic lifting body vehicle when under more variable and constrained condition in order to obtain the Pareto optimal solution of Common Aero Vehicle shape.
Numerical simulation-driven optimization of sheet metal drawing part shape
Institute of Scientific and Technical Information of China (English)
陈军; 石晓祥; 阮雪榆
2003-01-01
Numerical simulation and perturbation method were coupled into the iteration process for optimizing the sheet metal part stamping quality, by minimizing the risk of rupture, wrinkle and unstretched area. The optimization of the sheet metal drawing part surface was realized by adjusting the FEM node/element perturbation vector directions and values. The sweeping simplex algorithm was modified to better control the optimization process, and one-step simulation code was used to verify the new design formability. Finally, an autoauto fender drawing part shape optimization testified the proposed methods successfully.
Fine Extruding Deformation and Modeling Optimization of Die Cavityin Special-Shaped Products
Institute of Scientific and Technical Information of China (English)
Qi Hongyuan; Zhu Hengjun
2004-01-01
On the basis of Conformal Mapping theory, using approaches of numerical trigonometric interpolation and vector normal convergence, region function of three-dimension deforming, surface function of die cavity, and mapping function between the plastic flow model and the axis-symmetry model were set up respectively for fine extruding special-shaped products with different arc radius ri. Then the stream function and both fields of velocity and strain ratio are inferred for special-shaped plastic deformation; meanwhile, with the help of Upper-Bound principle, the parameter of die cavity gets optimized. Taking square-shaped and hexagon-shaped products with different arc radius ri as examples,the velocity field gets analyzed, the parameter of die cavity is optimized and the die cavity gets depicted as well. Consequently, above study provides theoretical support for achieving the technical goal of CAD/CAM integration in die cavity of fine extrusion.
Heat and mass transfer intensification and shape optimization a multi-scale approach
2013-01-01
Is the heat and mass transfer intensification defined as a new paradigm of process engineering, or is it just a common and old idea, renamed and given the current taste? Where might intensification occur? How to achieve intensification? How the shape optimization of thermal and fluidic devices leads to intensified heat and mass transfers? To answer these questions, Heat & Mass Transfer Intensification and Shape Optimization: A Multi-scale Approach clarifies the definition of the intensification by highlighting the potential role of the multi-scale structures, the specific interfacial area, the distribution of driving force, the modes of energy supply and the temporal aspects of processes. A reflection on the methods of process intensification or heat and mass transfer enhancement in multi-scale structures is provided, including porous media, heat exchangers, fluid distributors, mixers and reactors. A multi-scale approach to achieve intensification and shape optimization is developed and clearly expla...
Similar extrusion and mapping optimization of die cavity modeling for special-shaped products
Institute of Scientific and Technical Information of China (English)
QI Hong-yuan; WANG Shuang-xin; ZHU Heng-jun
2006-01-01
Aimed at the modeling issues in design and quick processing of extruding die for special-shaped products, with the help of Conformal Mapping theory, Conformal Mapping function is determined by the given method of numerical trigonometric interpolation. Three-dimensional forming problems are transformed into two-dimensional problems, and mathematical model of die cavity surface is established based on different kinds of vertical curve, as well as the mathematical model of plastic flow in extruding deformation of special-shaped products gets completed. By upper bound method, both vertical curves of die cavity and its parameters are optimized. Combining the optimized model with the latest NC technology, NC Program of die cavity and its CAM can be realized. Taking the similar extrusion of square-shaped products with arc radius as instance, both metal plastic similar extrusion and die cavity optimization are carried out.
Shape optimization and characterization of polysaccharide beads prepared by ionotropic gelation.
Smrdel, Polona; Bogataj, Marija; Zega, Anamarija; Planinsek, Odon; Mrhar, Ales
2008-03-01
The shape of drug loaded polysaccharide beads produced by ionotropic gelation has been optimized, with the aim of producing spherical beads suitable for further technological operations, such as coating. The optimization was performed on a model system sodium alginate/theophylline by inclusion of various fillers. Incorporation of excipients markedly influenced the morphological characteristics of the beads. The undesired irregular shape of beads caused by incorporation of the drug could only be improved by incorporating a combination of polycarbophil (PK) and polyvinylpyrrolidone (PVP). The spherical shape of these beads was stabilized mechanically by numerous air bubbles trapped inside the beads, which prevented the collapse of the beads during drying. The optimized method was shown to be applicable to a target system of pectin and an anti-inflammatory drug, LK-423.
Topology-optimized slow-light couplers for ring-shaped photonic crystal waveguide
DEFF Research Database (Denmark)
Pu, Minhao; Yang, Lirong; Frandsen, L. H.;
2010-01-01
We demonstrate a topology-optimized coupler for a ring-shaped photonic crystal waveguide to improve the coupling of light located in the slow-light regime. An enhancement of the coupling efficiency of up to 2.5 dB is experimentally demonstrated.......We demonstrate a topology-optimized coupler for a ring-shaped photonic crystal waveguide to improve the coupling of light located in the slow-light regime. An enhancement of the coupling efficiency of up to 2.5 dB is experimentally demonstrated....
Improving bending stress in spur gears using asymmetric gears and shape optimization
DEFF Research Database (Denmark)
Pedersen, Niels Leergaard
2010-01-01
Bending stress plays a significant role in gear design wherein its magnitude is controlled by the nominal bending stress and the stress concentration due to the geometrical shape. The bending stress is indirectly related to shape changes made to the cutting tool. This work shows that the bending...... stress can be reduced significantly by using asymmetric gear teeth and by shape optimizing the gear through changes made to the tool geometry. However, to obtain the largest possible stress reduction a custom tool must be designed depending on the number of teeth, but the stress reductions found...
Shape, position and orientational design of holes for plates with optimized eigenfrequencies
DEFF Research Database (Denmark)
Pedersen, Niels Leergaard; Pedersen, Pauli
2003-01-01
A hole with a given size is placed in the interior of a plate with an arbitrary external boundary. To avoid stress concentrations the shape of the hole must be smooth (continuous curvature). The objectives of the optimization are the eigenfrequencies of the plate with the hole. The optimization i...... on finite element analysis and sensitivity analysis. Mindlin plate theory is the basis for the FE-analysis and the semi-analytical sensitivity analysis includes only the elements on the boundary of the hole.......A hole with a given size is placed in the interior of a plate with an arbitrary external boundary. To avoid stress concentrations the shape of the hole must be smooth (continuous curvature). The objectives of the optimization are the eigenfrequencies of the plate with the hole. The optimization...
Bin-objective shape optimization based on linear programming model of arch dam
Institute of Scientific and Technical Information of China (English)
JIN Hai; LIN Gao; YANG Ming-sheng
2007-01-01
Bin-objective shape optimization of arch dam based on linear programming model is discussed to minimize both dam volume and maximal tensile stress. The importance of weight coefficient of the above two objectives is chosen according to the value of importance ratio. The influence of weight coefficient to the optimization result is discussed in detail and the numerical example shows that both the model and method proposed is doable.
Shape optimization of wire-wrapped fuel assembly using Kriging metamodeling technique
Energy Technology Data Exchange (ETDEWEB)
Raza, Wasim [Department of Mechanical Engineering, Inha University, 253 Yonghyun-Dong, Nam-Gu, Incheon 402-751 (Korea, Republic of); Kim, Kwang-Yong [Department of Mechanical Engineering, Inha University, 253 Yonghyun-Dong, Nam-Gu, Incheon 402-751 (Korea, Republic of)], E-mail: kykim@inha.ac.kr
2008-06-15
In this work, shape optimization of a wire-wrapped fuel assembly in a liquid metal reactor has been carried out by combining a three-dimensional Reynolds-averaged Navier-Stokes analysis with the Kriging method, a well-known metamodeling technique for optimization. Sequential quadratic programming (SQP) is used to search the optimal point from the constructed metamodel. Two geometric design variables are selected for the optimization and design space is sampled using Latin Hypercube Sampling (LHS). The optimization problem has been defined as a maximization of the objective function, which is as a linear combination of heat transfer and friction loss related terms with a weighing factor. The objective function value is more sensitive to the ratio of the wire spacer diameter to the fuel rod diameter than to the ratio of the wire wrap pitch to the fuel rod diameter. The optimal values of the design variables are obtained by varying the weighting factor.
Truncated acoustic black hole structure with the optimized tapering shape and damping coating
DEFF Research Database (Denmark)
Ih, Jeong-Guon; Kim, Miseong; Lee, Ik Jin
2016-01-01
The acoustic black hole (ABH) structure can be an option as a vibration damper by providing a tapered wedge at the end of a beam or plate. However, not much work has been done on design to yield an effective ABH design for such a plate. We attempt to optimize the shape of the ABH to effectively...
Forging tool shape optimization using pseudo inverse approach and adaptive incremental approach
Halouani, A.; Meng, F. J.; Li, Y. M.; Labergère, C.; Abbès, B.; Lafon, P.; Guo, Y. Q.
2013-05-01
This paper presents a simplified finite element method called "Pseudo Inverse Approach" (PIA) for tool shape design and optimization in multi-step cold forging processes. The approach is based on the knowledge of the final part shape. Some intermediate configurations are introduced and corrected by using a free surface method to consider the deformation paths without contact treatment. A robust direct algorithm of plasticity is implemented by using the equivalent stress notion and tensile curve. Numerical tests have shown that the PIA is very fast compared to the incremental approach. The PIA is used in an optimization procedure to automatically design the shapes of the preform tools. Our objective is to find the optimal preforms which minimize the equivalent plastic strain and punch force. The preform shapes are defined by B-Spline curves. A simulated annealing algorithm is adopted for the optimization procedure. The forging results obtained by the PIA are compared to those obtained by the incremental approach to show the efficiency and accuracy of the PIA.
Shape optimization of the stokes flow problem based on isogeometric analysis
DEFF Research Database (Denmark)
Park, Byong-Ug; Seo, Yu-Deok; Sigmund, Ole;
2013-01-01
Design-dependent loads related to boundary shape, such as pressure and convection loads, have been a challenging issue in optimization. Isogeometric analysis, where the analysis model has smooth boundaries described by spline functions can handle design-dependent loads with ease. In the present s...
Design Optimization of RFI Parameters by Manufacturing T-shaped Composite Panel
Institute of Scientific and Technical Information of China (English)
ZHANG Guo-li; HUANG Gu
2005-01-01
The aim of this project is to develop a novel approach for optimizing design resin film infusion (RFI) processing parameters by manufacturing T-shaped composite panel. The dimensional accuracy was selected as the objective function. By investigating the rheological properties of resin film, the compaction behavior of fiber preform and characteristics of RFI process, an optimal mathematical model was established, it was found that the numerical results obtained from the RFICOMP program package have good consistency with the experimental results, and this optimization procedure can be applied to other composites manufacture processes.
Special-shaped tube drawing forming and conformal optimization of die cavity
Institute of Scientific and Technical Information of China (English)
QI Hong-yuan; ZHU Heng-jun
2006-01-01
Aiming at the issues in quick processing and modeling design of drawing special-shaped tube die, by Conformal Mapping Theory and the numerical trigonometry method of interpolation between odd points and even points, the conformal mapping function is obtained. As the result, three-dimension drawing forming were converted into that of two-dimension problems, and the plastic stream function was analyzed, die cavity modeling and its optimized function were set up. Combining with modern processing technology, NC program and CAM of die cavity can be realized. Taking the drawing forming of hexagon tube with arc radii r and ellipse-shaped tube as instances, the drawing die cavity optimization of special-shaped tube was achieved, as well as, the changing principle of wall thickness was analyzed.
Stacking sequence and shape optimization of laminated composite plates via a level-set method
Allaire, G.; Delgado, G.
2016-12-01
We consider the optimal design of composite laminates by allowing a variable stacking sequence and in-plane shape of each ply. In order to optimize both variables we rely on a decomposition technique which aggregates the constraints into one unique constraint margin function. Thanks to this approach, an exactly equivalent bi-level optimization problem is established. This problem is made up of an inner level represented by the combinatorial optimization of the stacking sequence and an outer level represented by the topology and geometry optimization of each ply. We propose for the stacking sequence optimization an outer approximation method which iteratively solves a set of mixed integer linear problems associated to the evaluation of the constraint margin function. For the topology optimization of each ply, we lean on the level set method for the description of the interfaces and the Hadamard method for boundary variations by means of the computation of the shape gradient. Numerical experiments are performed on an aeronautic test case where the weight is minimized subject to different mechanical constraints, namely compliance, reserve factor and buckling load.
Optimal input shaping for Fisher identifiability of control-oriented lithium-ion battery models
Rothenberger, Michael J.
This dissertation examines the fundamental challenge of optimally shaping input trajectories to maximize parameter identifiability of control-oriented lithium-ion battery models. Identifiability is a property from information theory that determines the solvability of parameter estimation for mathematical models using input-output measurements. This dissertation creates a framework that exploits the Fisher information metric to quantify the level of battery parameter identifiability, optimizes this metric through input shaping, and facilitates faster and more accurate estimation. The popularity of lithium-ion batteries is growing significantly in the energy storage domain, especially for stationary and transportation applications. While these cells have excellent power and energy densities, they are plagued with safety and lifespan concerns. These concerns are often resolved in the industry through conservative current and voltage operating limits, which reduce the overall performance and still lack robustness in detecting catastrophic failure modes. New advances in automotive battery management systems mitigate these challenges through the incorporation of model-based control to increase performance, safety, and lifespan. To achieve these goals, model-based control requires accurate parameterization of the battery model. While many groups in the literature study a variety of methods to perform battery parameter estimation, a fundamental issue of poor parameter identifiability remains apparent for lithium-ion battery models. This fundamental challenge of battery identifiability is studied extensively in the literature, and some groups are even approaching the problem of improving the ability to estimate the model parameters. The first approach is to add additional sensors to the battery to gain more information that is used for estimation. The other main approach is to shape the input trajectories to increase the amount of information that can be gained from input
1944-02-01
torsional- divergente problem.which takes into.account the a.erod.ynadicspan - effect. The developments are-based on-the theory of tor- sion of straight...indicat-ethat neglect of the aerodynamic span effect may lead to an appreciable underestimation of the torsional- divergente velocity, the difference
Optimization of “T”-Shaped Fins Geometry Using Constructal Theory and “FEA” Concepts
Directory of Open Access Journals (Sweden)
ManasRanjanPadhy
2014-12-01
Full Text Available This paper reports the geometric (constructal optimization of T-shaped fin assemblies, where the objective is to maximize the global thermal conductance of the assembly, subject to total volume and fin-material constraints. Assemblies of plate fins are considered. It is shown that every geometric feature of the assembly is delivered by the optimization principle and the constraints. These optimal features are reported in dimensionless terms for this entire class of fin assemblies. Based on the constructal theory by Dr. A Bejan, T-shaped fins are developed for better heat conductance as compared to conventional fins. Now the geometry of this T type of fin contains many geometry parameters which affect the overall conductance of the fin. With the same material constraint and volume constraints optimal geometry ratios has been calculated so as to design the fin for its best performance. With focus to the practical situations and heat flow patterns, it is quite complex to calculate the temperatures on a T-shaped fin. It requires the help of FEA concepts and CAE software to optimize the geometry.
Adaptive feature selection using v-shaped binary particle swarm optimization
Dong, Hongbin; Zhou, Xiurong
2017-01-01
Feature selection is an important preprocessing method in machine learning and data mining. This process can be used not only to reduce the amount of data to be analyzed but also to build models with stronger interpretability based on fewer features. Traditional feature selection methods evaluate the dependency and redundancy of features separately, which leads to a lack of measurement of their combined effect. Moreover, a greedy search considers only the optimization of the current round and thus cannot be a global search. To evaluate the combined effect of different subsets in the entire feature space, an adaptive feature selection method based on V-shaped binary particle swarm optimization is proposed. In this method, the fitness function is constructed using the correlation information entropy. Feature subsets are regarded as individuals in a population, and the feature space is searched using V-shaped binary particle swarm optimization. The above procedure overcomes the hard constraint on the number of features, enables the combined evaluation of each subset as a whole, and improves the search ability of conventional binary particle swarm optimization. The proposed algorithm is an adaptive method with respect to the number of feature subsets. The experimental results show the advantages of optimizing the feature subsets using the V-shaped transfer function and confirm the effectiveness and efficiency of the feature subsets obtained under different classifiers. PMID:28358850
Shape optimization of phononic band gap structures using the homogenization approach
Vondřejc, Jaroslav; Heczko, Jan
2016-01-01
The paper deals with optimization of the acoustic band gaps computed using the homogenized model of strongly heterogeneous elastic composite which is constituted by soft inclusions periodically distributed in stiff elastic matrix. We employ the homogenized model of such medium to compute intervals - band gaps - of the incident wave frequencies for which acoustic waves cannot propagate. It was demonstrated that the band gaps distribution can be influenced by changing the shape of inclusions. Therefore, we deal with the shape optimization problem to maximize low-frequency band gaps; their bounds are determined by analyzing the effective mass tensor of the homogenized medium. Analytic transformation formulas are derived which describe dispersion effects of resizing the inclusions. The core of the problem lies in sensitivity of the eigenvalue problem associated with the microstructure. Computational sensitivity analysis is developed, which allows for efficient using of the gradient based optimization methods. Num...
Shape optimization of axisymmetric solids with the finite cell method using a fixed grid
Institute of Scientific and Technical Information of China (English)
Liang Meng; Wei-Hong Zhang; Ji-Hong Zhu; Zhao Xu; Shou-Hu Cai
2016-01-01
In this work, a design procedure extending the B-spline based finite cell method into shape optimization is developed for axisymmetric solids involving the centrifugal force effect. We first replace the traditional conforming mesh in the finite element method with structured cells that are fixed during the whole design process with a view to avoid the sophisticated re-meshing and eventual mesh distortion. Then, B-spline shape functions are further implemented to yield a high-order continuity field along the cell boundary in stress analysis. By means of the implicit description of the shape boundary, stress sensitivity is analytically derived with respect to shape design variables. Finally, we illustrate the efficiency and accuracy of the proposed protocol by several numerical test cases as well as a whole design procedure carried out on an aeronautic turbine disk.
Shape optimization of axisymmetric solids with the finite cell method using a fixed grid
Meng, Liang; Zhang, Wei-Hong; Zhu, Ji-Hong; Xu, Zhao; Cai, Shou-Hu
2016-06-01
In this work, a design procedure extending the B-spline based finite cell method into shape optimization is developed for axisymmetric solids involving the centrifugal force effect. We first replace the traditional conforming mesh in the finite element method with structured cells that are fixed during the whole design process with a view to avoid the sophisticated re-meshing and eventual mesh distortion. Then, B-spline shape functions are further implemented to yield a high-order continuity field along the cell boundary in stress analysis. By means of the implicit description of the shape boundary, stress sensitivity is analytically derived with respect to shape design variables. Finally, we illustrate the efficiency and accuracy of the proposed protocol by several numerical test cases as well as a whole design procedure carried out on an aeronautic turbine disk.
Ning, Xiaojuan; Wang, Yinghui; Meng, Weiliang; Zhang, Xiaopeng
2016-10-01
To understand and recognize the three-dimensional (3-D) objects represented as point cloud data, we use an optimized shape semantic graph (SSG) to describe 3-D objects. Based on the decomposed components of an object, the boundary surface of different components and the topology of components, the SSG gives a semantic description that is consistent with human vision perception. The similarity measurement of the SSG for different objects is effective for distinguishing the type of object and finding the most similar one. Experiments using a shape database show that the SSG is valuable for capturing the components of the objects and the corresponding relations between them. The SSG is not only suitable for an object without any loops but also appropriate for an object with loops to represent the shape and the topology. Moreover, a two-step progressive similarity measurement strategy is proposed to effectively improve the recognition rate in the shape database containing point-sample data.
Shape Optimization of Rotor Blade for Pulp Pressure Screen Based on FLUENT
Directory of Open Access Journals (Sweden)
Qu Qingwen
2013-10-01
Full Text Available The study got two modified blades by changing the structure and shape of the rotor blade of the pressure screen. Pulp flow field in the same condition is numerically simulated by the fluid dynamics software FLUENT. The pressure distribution is showed especially in the location of the sieve drum circle. The ideal blade structure is obtained by the pressure field compared with conventional blades. It has strong cleaning ability and not easy to blockage sieve drum. The shape of the rotor blade is optimized. The blade shape is analyzed to the influence law of energy consumption. It is proved that the new rotor has energy-saving advantages. It is significant to improve the performance of pulp screening equipment. The theoretical support for select of blade shape of bars is provided by analysis of flow field.
POEMS in Newton's Aerodynamic Frustum
Sampedro, Jaime Cruz; Tetlalmatzi-Montiel, Margarita
2010-01-01
The golden mean is often naively seen as a sign of optimal beauty but rarely does it arise as the solution of a true optimization problem. In this article we present such a problem, demonstrating a close relationship between the golden mean and a special case of Newton's aerodynamical problem for the frustum of a cone. Then, we exhibit a parallel…
Energy Technology Data Exchange (ETDEWEB)
Lee, Young Shin; Ryu, Chung Hyun [Chungnam National Univ., Taejon (Korea, Republic of)
2001-07-01
To reduce stress concentration around the intersection between a spherical pressure vessel and a cylindrical nozzle under various load conditions using less material, the optimization for the distribution of reinforcement has researched. The Ranked Bidirectional Evolutionary Structural Optimization(R-BESO) method is developed recently, which adds elements based on a rank, and the performance indicator which can estimate a fully stressed model. The R-BESO method can obtain the optimum design using less iteration number than iteration number of the BESO. In this paper, the optimized intersection shape is sought using R-BESO method for a flush and a protruding nozzle. The considered load cases are a radial compression, torque and shear force.
Mitigation of Power frequency Magnetic Fields. Using Scale Invariant and Shape Optimization Methods
Energy Technology Data Exchange (ETDEWEB)
Salinas, Ener; Yueqiang Liu; Daalder, Jaap; Cruz, Pedro; Antunez de Souza, Paulo Roberto Jr; Atalaya, Juan Carlos; Paula Marciano, Fabianna de; Eskinasy, Alexandre
2006-10-15
The present report describes the development and application of two novel methods for implementing mitigation techniques of magnetic fields at power frequencies. The first method makes use of scaling rules for electromagnetic quantities, while the second one applies a 2D shape optimization algorithm based on gradient methods. Before this project, the first method had already been successfully applied (by some of the authors of this report) to electromagnetic designs involving pure conductive Material (e.g. copper, aluminium) which implied a linear formulation. Here we went beyond this approach and tried to develop a formulation involving ferromagnetic (i.e. non-linear) Materials. Surprisingly, we obtained good equivalent replacement for test-transformers by varying the input current. In spite of the validity of this equivalence constrained to regions not too close to the source, the results can still be considered useful, as most field mitigation techniques are precisely developed for reducing the magnetic field in regions relatively far from the sources. The shape optimization method was applied in this project to calculate the optimal geometry of a pure conductive plate to mitigate the magnetic field originated from underground cables. The objective function was a weighted combination of magnetic energy at the region of interest and dissipated heat at the shielding Material. To our surprise, shapes of complex structure, difficult to interpret (and probably even harder to anticipate) were the results of the applied process. However, the practical implementation (using some approximation of these shapes) gave excellent experimental mitigation factors.
Goldberg, Kenneth A; Yashchuk, Valeriy V
2016-05-01
For glancing-incidence optical systems, such as short-wavelength optics used for nano-focusing, incorporating physical factors in the calculations used for shape optimization can improve performance. Wavefront metrology, including the measurement of a mirror's shape or slope, is routinely used as input for mirror figure optimization on mirrors that can be bent, actuated, positioned, or aligned. Modeling shows that when the incident power distribution, distance from focus, angle of incidence, and the spatially varying reflectivity are included in the optimization, higher Strehl ratios can be achieved. Following the works of Maréchal and Mahajan, optimization of the Strehl ratio (for peak intensity with a coherently illuminated system) occurs when the expectation value of the phase error's variance is minimized. We describe an optimization procedure based on regression analysis that incorporates these physical parameters. This approach is suitable for coherently illuminated systems of nearly diffraction-limited quality. Mathematically, this work is an enhancement of the methods commonly applied for ex situ alignment based on uniform weighting of all points on the surface (or a sub-region of the surface). It follows a similar approach to the optimization of apodized and non-uniformly illuminated optical systems. Significantly, it reaches a different conclusion than a more recent approach based on minimization of focal plane ray errors.
Meng, Fanjuan; Labergere, Carl; Lafon, Pascal
2011-05-01
In metal forming process, the forging die design is the most important step for products quality control. Reasonable dies shape can not only reduce raw material cost but also improving material flow and eliminating defects. The main objective of this paper is to obtain some optimal parameters of the initial billet and forging dies shape according to the simulation results of a two-step metal forming process (platting step and forging step). To develop this metal forming process optimization system several numerical tools are required: geometric modelling (CATIA V5™), FEM analysis (ABAQUS®), work-flow control and optimization computation (MODEFRONTIER®). This study is done in three stages: simulating the two-step metal forming process, building surrogate meta-models to relate response and variables and optimizing the process by using advanced optimization algorithms. In this paper, a two-step axisymmetric metal forming project was studied as an example. By using our simulation model, we get 581 correct real simulation results totally. According to all these real values, we build the surrogate meta-models and obtain Pareto points for a two-objective optimization process. The choice of a solution in all Pareto points will be done by the engineer who can choose his best values according to their criterions of project.
Institute of Scientific and Technical Information of China (English)
白俊强; 孙智伟; 董建鸿; 黄江涛
2015-01-01
在某典型运输机翼身组合体的构型上，进行了考虑机翼尾流影响的机身后体气动外形优化设计研究。基于翼身组合体构型建立了考虑尾流影响和部分工程约束的优化设计系统，并对后体构型在巡航状态下进行了优化设计。以比较适合描述后体变形的 NURBS 样条基函数为空间控制体属性引入 FFD 自由变形技术，通过在 FFD 控制框架对该运输机后体进行了空间属性构建。采用无限差值动网格技术提高空间网格的更新效率并保证网格质量。利用改进 Kriging 代理模型、量子粒子群优化算法提高优化效率和全局寻优能力。为减小巡航阻力，对某运输机后体的上翘角、截面形状等参数进行了优化设计，优化结果显示，设计后的机身气动特性明显提高。%The aerodynamic optimization design of typical transport afterbody considering the influence of the wing wake flow is studied.An optimization framework is established for the aircraft configuration and used for afterbody optimization at crui-sing status.The objective of this framework is to optimize the afterbody considering the influence from other parts of aircraft and the engineering constraints simultaneously.The spatial property of the afterbody in spatial control frame is established by implementing the free form deformation (FFD)approach.The NURBS spline is chosen as the basis function,which can represent the property of spatial control element and is suitable for afterbody geometry.Infinite interpolation deforming grid technique is adopted to update spatial grid with high efficiency and mesh quality.The modified Kriging surrogate model and quantum particle swarm algorithm are included in the optimization system to increase efficiency and ability to find global op-timal solution.In order to reduce drag at cruising status,upswept angle and cross section shape are optimized as the main afterbody configuration parameters
Whitehead, Allen H., Jr.
1989-01-01
This paper discusses the critical aerodynamic technologies needed to support the development of a class of aircraft represented by the National Aero-Space Plane (NASP). The air-breathing, single-stage-to-orbit mission presents a severe challenge to all of the aeronautical disciplines and demands an extension of the state-of-the-art in each technology area. While the largest risk areas are probably advanced materials and the development of the scramjet engine, there remains a host of design issues and technology problems in aerodynamics, aerothermodynamics, and propulsion integration. The paper presents an overview of the most significant propulsion integration problems, and defines the most critical fluid flow phenomena that must be evaluated, defined, and predicted for the class of aircraft represented by the Aero-Space Plane.
1979-02-01
Me 2 L~e coefficient de frottement CI est gnralement n~glig6. L’approximation est justifige par le fait que, qf , nul au recollement, est partout...be costly in terms of time and money. One should aim for a situation where an error of, say, 10% in estimating an aerodynamic coefficient or...constructing tables of forces and moments, or their coefficients , as functions of variables such as inci- dence angle, roll angle, speed and altitude, and
Topology Optimization of Shape Memory Alloy Actuators using Element Connectivity Parameterization
DEFF Research Database (Denmark)
Langelaar, Matthijs; Yoon, Gil Ho; Kim, Yoon Young;
2005-01-01
This paper presents the first application of topology optimization to the design of shape memory alloy actuators. Shape memory alloys (SMA’s) exhibit strongly nonlinear, temperature-dependent material behavior. The complexity in the constitutive behavior makes the topology design of SMA structures......-independent constitutive model of SMA’s is employed which allows efficient adjoint sensitivity analysis. The effectiveness of the proposed technique is illustrated by several numerical examples.In terms of computation time, the I-ECP method, a newly-developed version of ECP, is much more efficient because the degrees...
Study on methods of shape optimization and design of membrane mirror
Han, Su; Tan, Fanjiao; Wang, Dawei
2016-10-01
Based on the Karman's equation for circular thin plate and Qian's theory of membrane, the membrane mirror forming theory model is established. The effect of the high order disturbance for the shape of the membrane mirror is reduced by the way of variable thickness, so that the shape of the membrane is parabolic. The finite element method is used to verify the theory of the membrane mirror forming model. But the analysis results are not easy to convergence due to the flexibility characteristics of the membrane. So the reasonable solution parameters are necessary to ensure the correction of the finite element analysis result. The results show that the deviation between the finite element analysis and the theoretical results is small. The uniform thickness deviation is 0.73%, and the variable thickness deviation is 1.30%, thus the validity of the theoretical model is guaranteed. Then the membrane mirror design and optimization method is established on the basis of the theoretical model. Compare the theoretical surface and the optical design surface, and set the minimum root mean square error between the theoretical and the optical design surface as the optimization goal. The original shape and the surface shape control parameters of the membrane are optimized by using genetic algorithm. Finally, get the optimization model which can be used to optimize membrane mirror with any diameter. The genetic algorithm was used to optimize the thickness, boundary condition and the uniform loads. The result of membrane mirror accuracy is λ/4(λ=10um), which indicates that this membrane mirror can be applied in the infrared wavelength range for imaging. The main optimizing parameters are the variable thickness of the membrane, the boundary conditions and the surface loads. Finally, the optimization result of the membrane is the RMSmechanics of materials, this paper establishes a theoretical model and analyzes the relationship between the inflatable membrane mirror and the boundary
Shyshlov, Dmytro; Babikov, Dmitri
2012-11-21
In the context of molecular quantum computation the optimal control theory (OCT) is used to obtain shaped laser pulses for high-fidelity control of vibrational qubits. Optimization is done in time domain and the OCT algorithm varies values of electric field in each time step independently, tuning hundreds of thousands of parameters to find one optimal solution. Such flexibility is not available in experiments, where pulse shaping is done in frequency domain and the number of "tuning knobs" is much smaller. The question of possible experimental interpretations of theoretically found OCT solutions arises. In this work we analyze very accurate optimal pulse that we obtained for implementing quantum gate CNOT for the two-qubit system encoded into the exited vibrational states of thiophosgene molecule. Next, we try to alter this pulse by reducing the number of available frequency channels and intentionally introducing systematic and random errors (in frequency domain, by modifying the values of amplitudes and phases of different frequency components). We conclude that a very limited number of frequency components (only 32 in the model of thiophosgene) are really necessary for accurate control of the vibrational two-qubit system, and such pulses can be readily constructed using OCT. If the amplitude and phase errors of different frequency components do not exceed ±3% of the optimal values, one can still achieve accurate transformations of the vibrational two-qubit system, with gate fidelity of CNOT exceeding 0.99.
Shape optimization of plate with static and dynamic constralnts via virtual laminated element
Institute of Scientific and Technical Information of China (English)
李芳; 徐兴; 凌道盛
2003-01-01
The virtual laminated element method(VLEM) can resolve structural shape optimization problems with a new method.According to the characteristics of VLEM,only some characterized layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary.One of the important features of this method is that it is not necessary to regenerate the FE(finite element)grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements.The thickness distribution in thin plate optimization problems in other studies before is of stepped shape.However,in this paper,a continuous thickness distribution can be obtained after optimi-zation using VLEM,and is more reasonable.Furthermore,an approximate reanalysis method named "behavior model technique" can be used to reduce the amount of structural reanalysis.Sone typical examples are offered to prove the effectiveness and practicality of the proposed method.
Shape Optimization of A Turbine-99 Draft Tube Using Design-by-Morphing
Oh, Sahuck; Jiang, Chung-Hsiang; Marcus, Philip; Gutzwiller, David; Demeulenaere, Alain; Jiang, Chiyu
2016-11-01
We have found the "optimal" shape of a turbine-99 draft tube that maximizes its pressure recovery factor using a new design method called design-by- morphing. In design-by- morphing, new draft tubes are created by morphing multiple baseline draft tubes with different weights. The surfaces of baseline draft tubes are approximated by a summation of spectral coefficients multiplied by spectral basis functions. Then, a morphed draft tube is produced by computing a new set of spectral coefficients which are a weighted average of the spectral coefficients of the baseline draft tubes. The "optimal" draft tube is obtained by finding the weights such that the mean pressure recovery factor is maximized. After optimization is carried out using design-by- morphing, the high static pressure region is significantly reduced, and the flow is smoother and more uniform than it was in any of the baseline turbine-99 draft tubes. The optimal draft tube shows a 10.9% improvement over the turbine-99 draft tube. We have applied this method to trains and to aircrafts, and have reduced the drag and the drag-to-lift ratio by 13.2% and 23.1%, respectively. We believe that this optimization method is applicable to many engineering applications in which the performance of an object depends on its shape.
Application of genetic programming in shape optimization of concrete gravity dams by metaheuristics
Directory of Open Access Journals (Sweden)
Abdolhossein Baghlani
2014-12-01
Full Text Available A gravity dam maintains its stability against the external loads by its massive size. Hence, minimization of the weight of the dam can remarkably reduce the construction costs. In this paper, a procedure for finding optimal shape of concrete gravity dams with a computationally efficient approach is introduced. Genetic programming (GP in conjunction with metaheuristics is used for this purpose. As a case study, shape optimization of the Bluestone dam is presented. Pseudo-dynamic analysis is carried out on a total number of 322 models in order to establish a database of the results. This database is then used to find appropriate relations based on GP for design criteria of the dam. This procedure eliminates the necessity of the time-consuming process of structural analyses in evolutionary optimization methods. The method is hybridized with three different metaheuristics, including particle swarm optimization, firefly algorithm (FA, and teaching–learning-based optimization, and a comparison is made. The results show that although all algorithms are very suitable, FA is slightly superior to other two algorithms in finding a lighter structure in less number of iterations. The proposed method reduces the weight of dam up to 14.6% with very low computational effort.
Shaping the joint spectrum of down-converted photons through optimized custom poling
Dosseva, Annamaria; Cincio, Łukasz; Brańczyk, Agata M.
2016-01-01
We present a scheme for engineering the joint spectrum of photon pairs created via spontaneous parametric down-conversion. Our method relies on customizing the poling configuration of a quasi-phase-matched crystal. We use simulated annealing to find an optimized poling configuration which allows almost arbitrary shaping of the crystal's phase-matching function. This has direct application in the creation of pure single photons—currently one of the most important goals of single-photon quantum optics. We describe the general algorithm and provide code, written in C++, that outputs an optimized poling configuration given specific experimental parameters.
A New Application of an ANFIS for the Shape Optimal Design of Electromagnetic Devices
Directory of Open Access Journals (Sweden)
N. Mohdeb
2014-09-01
Full Text Available This paper presents a new model based on simulated annealing algorithm (ASA and adaptive neuro-fuzzy inference system (ANFIS for shape optimization and its applications to electromagnetic devices. The proposed model uses ANFIS system to evaluate the electromagnetic performance of the device. Both the ANFIS and ASA method are applied to the design/optimization of the electromagnetic actuator. The results of the proposed approach are compared with other techniques such as: method of moving asymptotes, penalty method, augmented lagrangian genetic algorithm and simulated annealing method (SA. Among the algorithms, the proposed ANFIS-ASA approach significantly outperforms the other methods.
A study of shape optimization on the metallic nanoparticles for thin-film solar cells.
Zhou, Shiwei; Huang, Xiaodong; Li, Qing; Xie, Yi Min
2013-10-29
The shape of metallic nanoparticles used to enhance the performance of thin-film solar cells is described by Gielis' superformula and optimized by an evolutionary algorithm. As a result, we have found a lens-like nanoparticle capable of improving the short circuit current density to 19.93 mA/cm2. Compared with a two-scale nanospherical configuration recently reported to synthesize the merits of large and small spheres into a single structure, the optimized nanoparticle enables the solar cell to achieve a further 7.75% improvement in the current density and is much more fabrication friendly due to its simple shape and tolerance to geometrical distortions.
Optimal sensor configuration for flexible structures with multi-dimensional mode shapes
Chang, Minwoo; Pakzad, Shamim N.
2015-05-01
A framework for deciding the optimal sensor configuration is implemented for civil structures with multi-dimensional mode shapes, which enhances the applicability of structural health monitoring for existing structures. Optimal sensor placement (OSP) algorithms are used to determine the best sensor configuration for structures with a priori knowledge of modal information. The signal strength at each node is evaluated by effective independence and modified variance methods. Euclidean norm of signal strength indices associated with each node is used to expand OSP applicability into flexible structures. The number of sensors for each method is determined using the threshold for modal assurance criterion (MAC) between estimated (from a set of observations) and target mode shapes. Kriging is utilized to infer the modal estimates for unobserved locations with a weighted sum of known neighbors. A Kriging model can be expressed as a sum of linear regression and random error which is assumed as the realization of a stochastic process. This study presents the effects of Kriging parameters for the accurate estimation of mode shapes and the minimum number of sensors. The feasible ranges to satisfy MAC criteria are investigated and used to suggest the adequate searching bounds for associated parameters. The finite element model of a tall building is used to demonstrate the application of optimal sensor configuration. The dynamic modes of flexible structure at centroid are appropriately interpreted into the outermost sensor locations when OSP methods are implemented. Kriging is successfully used to interpolate the mode shapes from a set of sensors and to monitor structures associated with multi-dimensional mode shapes.
SIMULTANEOUS SHAPE AND TOPOLOGY OPTIMIZATION OF TRUSS UNDER LOCAL AND GLOBAL STABILITY CONSTRAINTS
Institute of Scientific and Technical Information of China (English)
GuoXu; LiuWei; LiHongyan
2003-01-01
A new approach for the solution of truss shape and topology optimization problem sunder local and global stability constraints is proposed. By employing the cross sectional areas of each bar and some shape parameters as topology design variables, the difficulty arising from the jumping of buckling length phenomenon can be easily overcome without the necessity of introducing the overlapping bars into the initial ground structure. Therefore computational efforts can be saved for the solution of this kind of problem. By modifying the elements of the stiffness matrix using Sigmoid function, the continuity of the objective and constraint functions with respect to shape design parameters can be restored to some extent. Some numerical examples demonstrate the effectiveness of the proposed method.
Modeling and optimization of shape memory-superelastic antagonistic beam assembly
Tabesh, Majid; Elahinia, Mohammad H.
2010-04-01
Superelasticity (SE), shape memory effect (SM), high damping capacity, corrosion resistance, and biocompatibility are the properties of NiTi that makes the alloy ideal for biomedical devices. In this work, the 1D model developed by Brinson was modified to capture the shape memory effect, superelasticity and hysteresis behavior, as well as partial transformation in both positive and negative directions. This model was combined with the Euler beam equation which, by approximation, considers 1D compression and tension stress-strain relationships in different layers of a 3D beam assembly cross-section. A shape memory-superelastic NiTi antagonistic beam assembly was simulated with this model. This wire-tube assembly is designed to enhance the performance of the pedicle screws in osteoporotic bones. For the purpose of this study, an objective design is pursued aiming at optimizing the dimensions and initial configurations of the SMA wire-tube assembly.
Shapes and Shears, Stars and Smears Optimal Measurements for Weak Lensing
Bernstein, G M
2001-01-01
We present the theoretical and analytical bases of optimal techniques to measure weak gravitational shear from images of galaxies. We first characterize the geometric space of shears and ellipticity, then use this geometric interpretation to analyse images. The steps of this analysis include: measurement of object shapes on images, combining measurements of a given galaxy on different images, estimating the underlying shear from an ensemble of galaxy shapes, and compensating for the systematic effects of image distortion, bias from PSF asymmetries, and `"dilution" of the signal by the seeing. These methods minimize the ellipticity measurement noise, provide calculable shear uncertainty estimates, and allow removal of systematic contamination by PSF effects to arbitrary precision. Galaxy images and PSFs are decomposed into a family of orthogonal 2d Gaussian-based functions, making the PSF correction and shape measurement relatively straightforward and computationally efficient. We also discuss sources of noise...
How family status and social security claiming options shape optimal life cycle portfolios
Hubener, Andreas; Maurer, Raimond; Mitchell, Olivia S.
2013-01-01
Household decisions are profoundly shaped by a complex set of financial options due to Social Security rules determining retirement, spousal, and survivor benefits, along with benefit adjustments that vary with the age at which these are claimed. These rules influence optimal household asset allocation, insurance, and work decisions, given life cycle demographic shocks such as marriage, divorce, and children. Our model generates a wealth profile and a low and stable equity fraction consistent...
Shape optimization for viscous flows by reduced basis methods and free-form deformation
Manzoni, Andrea; Quarteroni, Alfio; Rozza, Gianluigi
2011-01-01
In this paper we further develop an approach previously introduced in [Lassila and Rozza, C.M.A.M.E 2010] for shape optimization that combines a suitable low-dimensional parametrization of the geometry (yielding a geometrical reduction) with reduced basis methods (yielding a reduction of computational complexity). More precisely, free-form deformation techniques are considered for the geometry description and its parametrization, while reduced basis methods are used upon a finite element dis...
Optimal Shape for Forces and Moments on a Multi-Element Hydrofoil
2007-10-01
Hydrofoil DISTRIBUTION: Approved for public release; distribution is unlimited. This paper is part of the following report: TITLE: International...Michigan, 5-8 August 2007 Optimal Shape for Forces and Moments on a Multi-Element Hydrofoil Yu-Tai Lee1, Vineet Ahuja 2, Ashvin Hosangadi 2 and Michael...forces and The Tab Assisted Control (TAC) foil used for moments acting on the hydrofoil with adequate underwater control surfaces, shown in Fig. la, was
Robotic U-shaped assembly line balancing using particle swarm optimization
Mukund Nilakantan, J.; Ponnambalam, S. G.
2016-02-01
Automation in an assembly line can be achieved using robots. In robotic U-shaped assembly line balancing (RUALB), robots are assigned to workstations to perform the assembly tasks on a U-shaped assembly line. The robots are expected to perform multiple tasks, because of their capabilities. U-shaped assembly line problems are derived from traditional assembly line problems and are relatively new. Tasks are assigned to the workstations when either all of their predecessors or all of their successors have already been assigned to workstations. The objective function considered in this article is to maximize the cycle time of the assembly line, which in turn helps to maximize the production rate of the assembly line. RUALB aims at the optimal assignment of tasks to the workstations and selection of the best fit robot to the workstations in a manner such that the cycle time is minimized. To solve this problem, a particle swarm optimization algorithm embedded with a heuristic allocation (consecutive) procedure is proposed. The consecutive heuristic is used to allocate the tasks to the workstation and to assign a best fit robot to that workstation. The proposed algorithm is evaluated using a wide variety of data sets. The results indicate that robotic U-shaped assembly lines perform better than robotic straight assembly lines in terms of cycle time.
The Optimization of a Shaped-Charge Design Using Parallel Computers
Energy Technology Data Exchange (ETDEWEB)
GARDNER,DAVID R.; VAUGHAN,COURTENAY T.
1999-11-01
Current supercomputers use large parallel arrays of tightly coupled processors to achieve levels of performance far surpassing conventional vector supercomputers. Shock-wave physics codes have been developed for these new supercomputers at Sandia National Laboratories and elsewhere. These parallel codes run fast enough on many simulations to consider using them to study the effects of varying design parameters on the performance of models of conventional munitions and other complex systems. Such studies maybe directed by optimization software to improve the performance of the modeled system. Using a shaped-charge jet design as an archetypal test case and the CTH parallel shock-wave physics code controlled by the Dakota optimization software, we explored the use of automatic optimization tools to optimize the design for conventional munitions. We used a scheme in which a lower resolution computational mesh was used to identify candidate optimal solutions and then these were verified using a higher resolution mesh. We identified three optimal solutions for the model and a region of the design domain where the jet tip speed is nearly optimal, indicating the possibility of a robust design. Based on this study we identified some of the difficulties in using high-fidelity models with optimization software to develop improved designs. These include developing robust algorithms for the objective function and constraints and mitigating the effects of numerical noise in them. We conclude that optimization software running high-fidelity models of physical systems using parallel shock wave physics codes to find improved designs can be a valuable tool for designers. While current state of algorithm and software development does not permit routine, ''black box'' optimization of designs, the effort involved in using the existing tools may well be worth the improvement achieved in designs.
Interactive Inverse Design Optimization of Fuselage Shape for Low-Boom Supersonic Concepts
Li, Wu; Shields, Elwood; Le, Daniel
2008-01-01
This paper introduces a tool called BOSS (Boom Optimization using Smoothest Shape modifications). BOSS utilizes interactive inverse design optimization to develop a fuselage shape that yields a low-boom aircraft configuration. A fundamental reason for developing BOSS is the need to generate feasible low-boom conceptual designs that are appropriate for further refinement using computational fluid dynamics (CFD) based preliminary design methods. BOSS was not developed to provide a numerical solution to the inverse design problem. Instead, BOSS was intended to help designers find the right configuration among an infinite number of possible configurations that are equally good using any numerical figure of merit. BOSS uses the smoothest shape modification strategy for modifying the fuselage radius distribution at 100 or more longitudinal locations to find a smooth fuselage shape that reduces the discrepancies between the design and target equivalent area distributions over any specified range of effective distance. For any given supersonic concept (with wing, fuselage, nacelles, tails, and/or canards), a designer can examine the differences between the design and target equivalent areas, decide which part of the design equivalent area curve needs to be modified, choose a desirable rate for the reduction of the discrepancies over the specified range, and select a parameter for smoothness control of the fuselage shape. BOSS will then generate a fuselage shape based on the designer's inputs in a matter of seconds. Using BOSS, within a few hours, a designer can either generate a realistic fuselage shape that yields a supersonic configuration with a low-boom ground signature or quickly eliminate any configuration that cannot achieve low-boom characteristics with fuselage shaping alone. A conceptual design case study is documented to demonstrate how BOSS can be used to develop a low-boom supersonic concept from a low-drag supersonic concept. The paper also contains a study
Scorer, R S
1958-01-01
Natural Aerodynamics focuses on the mathematics of any problem in air motion.This book discusses the general form of the law of fluid motion, relationship between pressure and wind, production of vortex filaments, and conduction of vorticity by viscosity. The flow at moderate Reynolds numbers, turbulence in a stably stratified fluid, natural exploitation of atmospheric thermals, and plumes in turbulent crosswinds are also elaborated. This text likewise considers the waves produced by thermals, transformation of thin layer clouds, method of small perturbations, and dangers of extra-polation.Thi
Tetrahedral Element Shape Optimization via the Jacobian Determinant and Condition Number
Energy Technology Data Exchange (ETDEWEB)
FREITAG,LORI A.; KNUPP,PATRICK
1999-09-27
We present a new shape measure for tetrahedral elements that is optimal in the sense that it gives the distance of a tetrahedron from the set of inverted elements. This measure is constructed from the condition number of the linear transformation between a unit equilateral tetrahedron and any tetrahedron with positive volume. We use this shape measure to formulate two optimization objective functions that are differentiated by their goal: the first seeks to improve the average quality of the tetrahedral mesh; the second aims to improve the worst-quality element in the mesh. Because the element condition number is not defined for tetrahedral with negative volume, these objective functions can be used only when the initial mesh is valid. Therefore, we formulate a third objective function using the determinant of the element Jacobian that is suitable for mesh untangling. We review the optimization techniques used with each objective function and present experimental results that demonstrate the effectiveness of the mesh improvement and untangling methods. We show that a combined optimization approach that uses both condition number objective functions obtains the best-quality meshes.
Tetrahedral element shape optimization via the Jacobian determinant and condition number.
Energy Technology Data Exchange (ETDEWEB)
Freitag, L. A.; Knupp, P. M.
1999-07-30
We present a new shape measure for tetrahedral elements that is optimal in the sense that it gives the distance of a tetrahedron from the set of inverted elements. This measure is constructed from the condition number of the linear transformation between a unit equilateral tetrahedron and any tetrahedron with positive volume. We use this shape measure to formulate two optimization objective functions that are differentiated by their goal: the first seeks to improve the average quality of the tetrahedral mesh; the second aims to improve the worst-quality element in the mesh. Because the element condition number is not defined for tetrahedral with negative volume, these objective functions can be used only when the initial mesh is valid. Therefore, we formulate a third objective function using the determinant of the element Jacobian that is suitable for mesh untangling. We review the optimization techniques used with each objective function and present experimental results that demonstrate the effectiveness of the mesh improvement and untangling methods. We show that a combined optimization approach that uses both condition number objective functions obtains the best-quality meshes.
Galvan-Sosa, M.; Portilla, J.; Hernandez-Rueda, J.; Siegel, J.; Moreno, L.; Ruiz de la Cruz, A.; Solis, J.
2014-02-01
Femtosecond laser pulse temporal shaping techniques have led to important advances in different research fields like photochemistry, laser physics, non-linear optics, biology, or materials processing. This success is partly related to the use of optimal control algorithms. Due to the high dimensionality of the solution and control spaces, evolutionary algorithms are extensively applied and, among them, genetic ones have reached the status of a standard adaptive strategy. Still, their use is normally accompanied by a reduction of the problem complexity by different modalities of parameterization of the spectral phase. Exploiting Rabitz and co-authors' ideas about the topology of quantum landscapes, in this work we analyze the optimization of two different problems under a deterministic approach, using a multiple one-dimensional search (MODS) algorithm. In the first case we explore the determination of the optimal phase mask required for generating arbitrary temporal pulse shapes and compare the performance of the MODS algorithm to the standard iterative Gerchberg-Saxton algorithm. Based on the good performance achieved, the same method has been applied for optimizing two-photon absorption starting from temporally broadened laser pulses, or from laser pulses temporally and spectrally distorted by non-linear absorption in air, obtaining similarly good results which confirm the validity of the deterministic search approach.
Shape Optimization of the Turbomachine Channel by a Gradient Method -Accuracy Improvement
Institute of Scientific and Technical Information of China (English)
Marek Rabiega
2003-01-01
An algorithm of the gradient method of the channel shape optimization has been built on the basis of 3D equations of mass, momentum and energy conservation in the fluid flow. The gradient of the functional that is posed for minimization has been calculated by two methods, via sensitivities and - for comparison - by the finite difference approximation. The equations for sensitivities have been generated through a differentiate-then-discretize approach. The exemplary optimization of the blade shape of the centrifugal compressor wheel has been carried out for the inviscid gas flow governed by Euler equations with a non-uniform mass flow distribution as the inlet boundary condition. Mixing losses have been minimized downstream the outlet of the centrifugal wheel in this exemplary optimization. The results of the optimization problem accomplished by the two above-mentioned methods have been presented. In the case sparse grids have been used, the method with the gradient approximated by finite differences has been found to be more consistent. The discretization accuracy has turned out to be crucial for the consistency of the gradient method via sensitivities.
Process Optimization for Suppressing Cracks in Laser Engineered Net Shaping of Al2O3 Ceramics
Niu, F. Y.; Wu, D. J.; Yan, S.; Ma, G. Y.; Zhang, B.
2017-03-01
Direct additive manufacturing of ceramics (DAMC) without binders is a promising technique for rapidly fabricating high-purity components with good performance. Nevertheless, cracks are easily generated during fabrication as a result of the high intrinsic brittleness of ceramics and the great temperature gradients. Therefore, optimizing the DAMC process is a challenge. In this study, direct fabrication of Al2O3 single-bead wall structures are conducted with a laser engineered net shaping (LENS) system. A new process optimization method for suppressing cracks is proposed based on analytical models, and then the influence of process parameters on crack number is discussed experimentally. The results indicate that the crack number decreases obviously with the increase of scanning speed. Single-bead wall specimens without cracks are successfully fabricated by the optimized process.
An Improved Chaos Genetic Algorithm for T-Shaped MIMO Radar Antenna Array Optimization
Directory of Open Access Journals (Sweden)
Xin Fu
2014-01-01
Full Text Available In view of the fact that the traditional genetic algorithm easily falls into local optimum in the late iterations, an improved chaos genetic algorithm employed chaos theory and genetic algorithm is presented to optimize the low side-lobe for T-shaped MIMO radar antenna array. The novel two-dimension Cat chaotic map has been put forward to produce its initial population, improving the diversity of individuals. The improved Tent map is presented for groups of individuals of a generation with chaos disturbance. Improved chaotic genetic algorithm optimization model is established. The algorithm presented in this paper not only improved the search precision, but also avoids effectively the problem of local convergence and prematurity. For MIMO radar, the improved chaos genetic algorithm proposed in this paper obtains lower side-lobe level through optimizing the exciting current amplitude. Simulation results show that the algorithm is feasible and effective. Its performance is superior to the traditional genetic algorithm.
A Rapid Aerodynamic Design Procedure Based on Artificial Neural Networks
Rai, Man Mohan
2001-01-01
An aerodynamic design procedure that uses neural networks to model the functional behavior of the objective function in design space has been developed. This method incorporates several improvements to an earlier method that employed a strategy called parameter-based partitioning of the design space in order to reduce the computational costs associated with design optimization. As with the earlier method, the current method uses a sequence of response surfaces to traverse the design space in search of the optimal solution. The new method yields significant reductions in computational costs by using composite response surfaces with better generalization capabilities and by exploiting synergies between the optimization method and the simulation codes used to generate the training data. These reductions in design optimization costs are demonstrated for a turbine airfoil design study where a generic shape is evolved into an optimal airfoil.
Development of a fast shape memory alloy based actuator for morphing airfoils
Lara-Quintanilla, A.
2016-01-01
The design of aerodynamic airfoils are optimized for certain conditions. For instance, the shape of the wings of fixed-wing aircrafts are designed and optimized for a certain flight condition (in terms of altitude, speed, aircraft weight, etc.). However, these flight conditions vary significantly du
Shape Optimization of Three-Way Reversing Valve for Cavitation Reduction
Energy Technology Data Exchange (ETDEWEB)
Lee, Myeong Gon; Han, Seung Ho [Donga Univ., Busan (Korea, Republic of); Lim, Cha Suk [Baek San Hi-Tech Co., Ltd., Seoul (Korea, Republic of)
2015-11-15
A pair of two-way valves typically is used in automotive washing machines, where the water flow direction is frequently reversed and highly pressurized clean water is sprayed to remove the oil and dirt remaining on machined engine and transmission blocks. Although this valve system has been widely used because of its competitive price, its application is sometimes restricted by surging effects, such as pressure ripples occurring in rapid changes in water flow caused by inaccurate valve control. As an alternative, one three-way reversing valve can replace the valve system because it provides rapid and accurate changes to the water flow direction without any precise control device. However, a cavitation effect occurs because of the complicated bottom plug shape of the valve. In this study, the cavitation index and percent of cavitation (POC) were introduced to numerically evaluate fluid flows via computational fluid dynamics (CFD) analysis. To reduce the cavitation effect generated by the bottom plug, the optimal shape design was carried out through a parametric study, in which a simple computer-aided engineering (CAE) model was applied to avoid time consuming CFD analysis and difficulties in achieving convergence. The optimal shape design process using full factorial design of experiments (DOEs) and an artificial neural network meta-model yielded the optimal waist and tail length of the bottom plug with a POC value of less than 30%, which meets the requirement of no cavitation occurrence. The optimal waist length, tail length and POC value were found to 6.42 mm, 6.96 mm and 27%, respectively.
Shape optimization of three-way reversing valve for cavitation reduction
Energy Technology Data Exchange (ETDEWEB)
Lee, Myeong Gon; Han, Seung Ho [Dept. of Mechanical Engineering, Dong-A University, Busan (Korea, Republic of); Lim, Cha Suk [Baek San Hi-Tech Co., Ltd., Yangsan(Korea, Republic of)
2015-11-15
A pair of two-way valves typically is used in automotive washing machines, where the water flow direction is frequently reversed and highly pressurized clean water is sprayed to remove the oil and dirt remaining on machined engine and transmission blocks. Although this valve system has been widely used because of its competitive price, its application is sometimes restricted by surging effects, such as pressure ripples occurring in rapid changes in water flow caused by inaccurate valve control. As an alternative, one three-way reversing valve can replace the valve system because it provides rapid and accurate changes to the water flow direction without any precise control device. However, a cavitation effect occurs because of the complicated bottom plug shape of the valve. In this study, the cavitation index and percent of cavitation (POC) were introduced to numerically evaluate fluid flows via computational fluid dynamics (CFD) analysis. To reduce the cavitation effect generated by the bottom plug, the optimal shape design was carried out through a parametric study, in which a simple computer-aided engineering (CAE) model was applied to avoid time-consuming CFD analysis and difficulties in achieving convergence. The optimal shape design process using full factorial design of experiments (DOEs) and an artificial neural network meta-model yielded the optimal waist and tail length of the bottom plug with a POC value of less than 30%, which meets the requirement of no cavitation occurrence. The optimal waist length, tail length and POC value were found to 6.42 mm, 6.96 mm and 27%, respectively.
Aerodynamics Research Revolutionizes Truck Design
2008-01-01
During the 1970s and 1980s, researchers at Dryden Flight Research Center conducted numerous tests to refine the shape of trucks to reduce aerodynamic drag and improved efficiency. During the 1980s and 1990s, a team based at Langley Research Center explored controlling drag and the flow of air around a moving body. Aeroserve Technologies Ltd., of Ottawa, Canada, with its subsidiary, Airtab LLC, in Loveland, Colorado, applied the research from Dryden and Langley to the development of the Airtab vortex generator. Airtabs create two counter-rotating vortices to reduce wind resistance and aerodynamic drag of trucks, trailers, recreational vehicles, and many other vehicles.
Institute of Scientific and Technical Information of China (English)
Honglei ZHAO; Songtao WANG; Wanjin HAN; Guotai FENG
2008-01-01
A three-stage axial turbine was redesigned by jointly applying S2 flow surface direct problem calculation methods and multistage local optimization methods. A genetic algorithm and artificial neural network were jointly adopted during optimization. A three-dimensional viscosity Navier-Stokes equation solver was applied for flow computation. H-O-H-topology grid was adopted as computation grid, that is, an H-topology grid was adopted for inlet and outlet segment, whereas an O-topology grid was adopted for stator zone and rotor zone. Through the optimization design, the total efficiency increases 1.1%, thus indicating that the total performance is improved and the design objective is achieved.
兆瓦级风电机组叶片气动外形技术研究%Aerodynamic Shape Study of a MW- sized Wind Turbine Blade with Horizontal Axis
Institute of Scientific and Technical Information of China (English)
刘文芝; 齐向东; 周洁; 巩勇智; 张富海
2011-01-01
针对大型风电机组叶片最佳设计攻角、升力系数呈非线性变化问题,基于叶素-动量理论,通过改进Wilson优化算法,从结构及加工角度修正翼型,设计了1.2 MW风电机组叶片的气动外形.通过片条理论进行气动性能的计算,求出不同风速下改变的变化桨距角,得到其功率曲线,证明了用改进的Wilson算法的合理性和以之设计大型风电机组叶片气动外形的可行性.%The optimum design angle of attack for large - scale wind turbine blade and the lift coefficient assumes the nonlinearities change. For such problem, 1.2 MW wind turbine blade's profile is designed based on BEM theory through improving on the Wilson algorithm and correcting the airfoil from the structure and processing angle. By strip theory and the calculation for the aerodynamic performance, the changeable pitch angle varied with different wind speed is solved and the power curve is gotten, which proves the rationality of improving on the Wilson algorithm and the feasibility of designing Aerodynamic shape of large - scale wind turbine blade with horizontal axis.
Lee, Dae Young
The design of a small satellite is challenging since they are constrained by mass, volume, and power. To mitigate these constraint effects, designers adopt deployable configurations on the spacecraft that result in an interesting and difficult optimization problem. The resulting optimization problem is challenging due to the computational complexity caused by the large number of design variables and the model complexity created by the deployables. Adding to these complexities, there is a lack of integration of the design optimization systems into operational optimization, and the utility maximization of spacecraft in orbit. The developed methodology enables satellite Multidisciplinary Design Optimization (MDO) that is extendable to on-orbit operation. Optimization of on-orbit operations is possible with MDO since the model predictive controller developed in this dissertation guarantees the achievement of the on-ground design behavior in orbit. To enable the design optimization of highly constrained and complex-shaped space systems, the spherical coordinate analysis technique, called the "Attitude Sphere", is extended and merged with an additional engineering tools like OpenGL. OpenGL's graphic acceleration facilitates the accurate estimation of the shadow-degraded photovoltaic cell area. This technique is applied to the design optimization of the satellite Electric Power System (EPS) and the design result shows that the amount of photovoltaic power generation can be increased more than 9%. Based on this initial methodology, the goal of this effort is extended from Single Discipline Optimization to Multidisciplinary Optimization, which includes the design and also operation of the EPS, Attitude Determination and Control System (ADCS), and communication system. The geometry optimization satisfies the conditions of the ground development phase; however, the operation optimization may not be as successful as expected in orbit due to disturbances. To address this issue
DEFF Research Database (Denmark)
Henrichsen, Søren Randrup; Lindgaard, Esben; Lund, Erik
2015-01-01
Robust buckling optimal design of laminated composite structures is conducted in this work. Optimal designs are obtained by considering geometric imperfections in the optimization procedure. Discrete Material Optimization is applied to obtain optimal laminate designs. The optimal geometric...... example. The imperfection sensitivity of the optimized structure decreases during the recurrence optimization for both examples, hence robust buckling optimal structures are designed....
Directory of Open Access Journals (Sweden)
Nitish Katal
2016-01-01
Full Text Available Automation of the robust control system synthesis for uncertain systems is of great practical interest. In this paper, the loop shaping step for synthesizing quantitative feedback theory (QFT based controller for a two-phase permanent magnet stepper motor (PMSM has been automated using teaching learning-based optimization (TLBO algorithm. The QFT controller design problem has been posed as an optimization problem and TLBO algorithm has been used to minimize the proposed cost function. This facilitates designing low-order fixed-structure controller, eliminates the need of manual loop shaping step on the Nichols charts, and prevents the overdesign of the controller. A performance comparison of the designed controller has been made with the classical PID tuning method of Ziegler-Nichols and QFT controller tuned using other optimization algorithms. The simulation results show that the designed QFT controller using TLBO offers robust stability, disturbance rejection, and proper reference tracking over a range of PMSM’s parametric uncertainties as compared to the classical design techniques.
Packing Optimization of Sorbent Bed Containing Dissimilar and Irregular Shaped Media
Holland, Nathan; Guttromson, Jayleen; Piowaty, Hailey
2011-01-01
The Fire Cartridge is a packed bed air filter with two different and separate layers of media designed to provide respiratory protection from combustion products after a fire event on the International Space Station (ISS). The first layer of media is a carbon monoxide catalyst and the second layer of media is universal carbon. During development of Fire Cartridge prototypes, the two media beds were noticed to have shifted inside the cartridge. The movement of media within the cartridge can cause mixing of the bed layers, air voids, and channeling, which could cause preferential air flow and allow contaminants to pass through without removal. An optimally packed bed mitigates these risks and ensures effective removal of contaminants from the air. In order to optimally pack each layer, vertical, horizontal, and orbital agitations were investigated and a packed bulk density was calculated for each method. Packed bulk density must be calculated for each media type to accommodate variations in particle size, shape, and density. Additionally, the optimal vibration parameters must be re-evaluated for each batch of media due to variations in particle size distribution between batches. For this application it was determined that orbital vibrations achieve an optimal pack density and the two media layers can be packed by the same method. Another finding was media with a larger size distribution of particles achieve an optimal bed pack easier than media with a smaller size distribution of particles.
Meshless shape design sensitivity analysis and optimization for contact problem with friction
Kim, N. H.; Choi, K. K.; Chen, J. S.; Park, Y. H.
In this paper, a continuum-based shape design sensitivity formulation for a frictional contact problem with a rigid body is proposed using a meshless method. The contact condition is imposed using the penalty method that regularizes the solution of variational inequality. The shape dependency of the contact variational form with respect to the design velocity field is obtained. The dependency of the response with respect to the shape of the rigid body is also considered. It is shown that the sensitivity equation needs to be solved at the final converged load step for the frictionless contact problem, whereas for the frictional contact case the sensitivity solution is needed at the converged configuration of each load step because the sensitivity of the current load step depends on that of the previous load step. The continuum-based contact formulation and consistent linearization is critical for accurate shape design sensitivity results. The accuracy of the proposed method is compared with the finite difference result and excellent agreement is obtained for a door seal contact example. A design optimization problem is formulated and solved to reduce the contact gap opening successfully in a demonstration of the proposed method.
Adjoint-based shape optimization of fin geometry for enhanced solid/liquid phase-change process
Morimoto, Kenichi; Suzuki, Yuji
2015-11-01
In recent years, the control of heat transfer processes, which play a critical role in various engineering devices/systems, has gained renewed attention. The present study aims to establish an adjoint-based shape optimization method for high-performance heat transfer processes involving phase-change phenomena. A possible example includes the application to the thermal management technique using phase-change material. Adjoint-based shape optimization scheme is useful to optimal shape design and optimal control of systems, for which the base function of the solution is unknown and the solution includes an infinite number of degrees of freedom. Here we formulate the shape-optimization scheme based on adjoint heat conduction analyses, focusing on the shape optimization of fin geometry. In the computation of the developed scheme, a meshless local Petrov-Galerkin (MLPG) method that is suited for dealing with complex boundary geometry is employed, and the enthalpy method is adopted for analyzing the motion of the phase-change interface. We examine in detail the effect of the initial geometry and the node distribution in the MLPG analysis upon the final solution of the shape optimization. Also, we present a new strategy for the computation using bubble mesh.
Kanno, Masaaki; Hara, Shinji
2012-01-01
This paper proposes a plant/controller design integration method for H_∞ loop-shaping design based on symbolic-numeric hybrid optimization. This approach firstly employs parametric polynomial spectral factorization to accomplish parametric optimization and derive an expression for the optimal cost. Owing to the obtained expression, sensitivity analysis of the achievable performance level with respect to plant parameters is amenable, which allows numerical optimization methods to seek the opti...
Energy-optimal electrical-stimulation pulses shaped by the Least-Action Principle.
Directory of Open Access Journals (Sweden)
Nedialko I Krouchev
Full Text Available Electrical stimulation (ES devices interact with excitable neural tissue toward eliciting action potentials (AP's by specific current patterns. Low-energy ES prevents tissue damage and loss of specificity. Hence to identify optimal stimulation-current waveforms is a relevant problem, whose solution may have significant impact on the related medical (e.g. minimized side-effects and engineering (e.g. maximized battery-life efficiency. This has typically been addressed by simulation (of a given excitable-tissue model and iterative numerical optimization with hard discontinuous constraints--e.g. AP's are all-or-none phenomena. Such approach is computationally expensive, while the solution is uncertain--e.g. may converge to local-only energy-minima and be model-specific. We exploit the Least-Action Principle (LAP. First, we derive in closed form the general template of the membrane-potential's temporal trajectory, which minimizes the ES energy integral over time and over any space-clamp ionic current model. From the given model we then obtain the specific energy-efficient current waveform, which is demonstrated to be globally optimal. The solution is model-independent by construction. We illustrate the approach by a broad set of example situations with some of the most popular ionic current models from the literature. The proposed approach may result in the significant improvement of solution efficiency: cumbersome and uncertain iteration is replaced by a single quadrature of a system of ordinary differential equations. The approach is further validated by enabling a general comparison to the conventional simulation and optimization results from the literature, including one of our own, based on finite-horizon optimal control. Applying the LAP also resulted in a number of general ES optimality principles. One such succinct observation is that ES with long pulse durations is much more sensitive to the pulse's shape whereas a rectangular pulse is most
Institute of Scientific and Technical Information of China (English)
QI Hong-yuan; ZHU Heng-jun
2004-01-01
With the help of Complex Function Mapping theory, the complicated three-dimensional deformation problems are transferred into two-dimensional problems, and the function of strain ratio field is analyzed in the metal plastic extruding deformation. Taking the strain-hardening effect of metal deformation into account, the relationship between friction behavior and optimized mathematical model is analyzed by the numerical analysis friction energy dissipation function. As a result, the method of lowering the material hardening and decreasing the reduction ratio over multi-procedures can be used to improve the surface quality of metal special-shape extrusion products.
Parametric geometric model and shape optimization of an underwater glider with blended-wing-body
Sun, Chunya; Song, Baowei; Wang, Peng
2015-11-01
Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB), is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD) code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO), is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.
Optimal Neutron Source and Beam Shaping Assembly for Boron Neutron Capture Therapy
Vujic, J L; Greenspan, E; Guess, S; Karni, Y; Kastenber, W E; Kim, L; Leung, K N; Regev, D; Verbeke, J M; Waldron, W L; Zhu, Y
2003-01-01
There were three objectives to this project: (1) The development of the 2-D Swan code for the optimization of the nuclear design of facilities for medical applications of radiation, radiation shields, blankets of accelerator-driven systems, fusion facilities, etc. (2) Identification of the maximum beam quality that can be obtained for Boron Neutron Capture Therapy (BNCT) from different reactor-, and accelerator-based neutron sources. The optimal beam-shaping assembly (BSA) design for each neutron source was also to e obtained. (3) Feasibility assessment of a new neutron source for NCT and other medical and industrial applications. This source consists of a state-of-the-art proton or deuteron accelerator driving and inherently safe, proliferation resistant, small subcritical fission assembly.
Shaping femtosecond coherent anti-Stokes Raman spectra using optimal control theory.
Pezeshki, Soroosh; Schreiber, Michael; Kleinekathöfer, Ulrich
2008-04-21
Optimal control theory is used to tailor laser pulses which enhance a femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) spectrum in a certain frequency range. For this aim the optimal control theory has to be applied to a target state distributed in time. Explicit control mechanisms are given for shaping either the Stokes or the probe pulse in the four-wave mixing process. A simple molecule for which highly accurate potential energy surfaces are available, namely molecular iodine, is used to test the procedure. This approach of controlling vibrational motion and delivering higher intensities to certain frequency ranges might also be important for the improvement of CARS microscopy.
Optimal Neutron Source & Beam Shaping Assembly for Boron Neutron Capture Therapy
Energy Technology Data Exchange (ETDEWEB)
J. Vujic; E. Greenspan; W.E. Kastenber; Y. Karni; D. Regev; J.M. Verbeke, K.N. Leung; D. Chivers; S. Guess; L. Kim; W. Waldron; Y. Zhu
2003-04-30
There were three objectives to this project: (1) The development of the 2-D Swan code for the optimization of the nuclear design of facilities for medical applications of radiation, radiation shields, blankets of accelerator-driven systems, fusion facilities, etc. (2) Identification of the maximum beam quality that can be obtained for Boron Neutron Capture Therapy (BNCT) from different reactor-, and accelerator-based neutron sources. The optimal beam-shaping assembly (BSA) design for each neutron source was also to e obtained. (3) Feasibility assessment of a new neutron source for NCT and other medical and industrial applications. This source consists of a state-of-the-art proton or deuteron accelerator driving and inherently safe, proliferation resistant, small subcritical fission assembly.
Surrogate modelling and optimization using shape-preserving response prediction: A review
Leifsson, Leifur; Koziel, Slawomir
2016-03-01
Computer simulation models are ubiquitous in modern engineering design. In many cases, they are the only way to evaluate a given design with sufficient fidelity. Unfortunately, an added computational expense is associated with higher fidelity models. Moreover, the systems being considered are often highly nonlinear and may feature a large number of designable parameters. Therefore, it may be impractical to solve the design problem with conventional optimization algorithms. A promising approach to alleviate these difficulties is surrogate-based optimization (SBO). Among proven SBO techniques, the methods utilizing surrogates constructed from corrected physics-based low-fidelity models are, in many cases, the most efficient. This article reviews a particular technique of this type, namely, shape-preserving response prediction (SPRP), which works on the level of the model responses to correct the underlying low-fidelity models. The formulation and limitations of SPRP are discussed. Applications to several engineering design problems are provided.
Zeng, Y. P.; Dong, J. L.; He, T. D.; Wang, B.
2016-08-01
Low qualified rate and inferior quality frequently occurring in the general deep drawing process of a certain box-shaped part, now use hydroforming to optimize forming process, in order to study the effect of hydroforming for improving the quality and formability, purposed five process schemes: general deep drawing, active hydroforming, passive hydroforming, general deep drawing combined with active hydroforming, passive combined with active hydroforming. Each process was simulated by finite element simulation and results were analysed. The results indicate the passive combined with active hydroforming is the best scheme which can obtain smallest thickness thinning and satisfactory formability, then optimized hydroforming pressure, blank holder force subsequently by adjust the simulation parameters. Research result proves that active/passive hydroforming is a new method for complex parts forming.
Shape and Topology Optimization in Stokes Flow with a Phase Field Approach
Energy Technology Data Exchange (ETDEWEB)
Garcke, Harald, E-mail: harald.garcke@mathematik.uni-regensburg.de; Hecht, Claudia, E-mail: claudia.hecht@mathematik.uni-regensburg.de [Universität Regensburg, Fakultät für Mathematik (Germany)
2016-02-15
In this paper we introduce a new formulation for shape optimization problems in fluids in a diffuse interface setting that can in particular handle topological changes. By adding the Ginzburg–Landau energy as a regularization to the objective functional and relaxing the non-permeability outside the fluid region by introducing a porous medium approach we hence obtain a phase field problem where the existence of a minimizer can be guaranteed. This problem is additionally related to a sharp interface problem, where the permeability of the non-fluid region is zero. In both the sharp and the diffuse interface setting we can derive necessary optimality conditions using only the natural regularity of the minimizers. We also pass to the limit in the first order conditions.
Institute of Scientific and Technical Information of China (English)
蒙文巩; 马东立
2013-01-01
在现代大型客机系列的设计中,机翼常作为通用模块,在每个型号上使用.针对各个型号因使用任务要求不同而使得对机翼气动特性需求不同的问题,引入设计权重,提出机翼气动特性匹配设计概念,建立了机翼气动特性匹配设计模型.并分析了设计权重的不确定性对机翼气动特性的影响,建立了稳健匹配优化设计模型,最终完成某高亚音速客机系列机翼气动特性稳健匹配优化设计.研究结果表明:与传统优化方法相比,稳健优化设计能够减小飞机系列中机翼在各型号上的气动特性差异,降低了设计权重的不确定性对机翼气动特性的影响,提高了飞机系列的气动性能.%The wing component is served as a common module and sharing in every model of modern aircraft family. Due to the different mission of every model, the aerodynamic requirement of wing in the aircraft family is different. The design-ratio was inducted and the matching design optimization concept for the wing aerodynamic characteristics was presented. The corresponding models with the parameter of the model design-ratio were established. The impact of the uncertainty of the design-ratio acting on the wing aerodynamic was analyzed. The model of robust matching design optimization (RMDO) for the functional module characteristics of the aircraft family was built. RMDO for the wing aerodynamic characteristics of a transonic aircraft family with two models was accomplished. The results indicate that the wing aerodynamic difference of every model in the aircraft family and the impact of the uncertainty of the design-ratio acting on the wing aerodynamic reduce based on RMDO. And the aerodynamic performance of the aircraft is improved.
Genetic Algorithm Optimization of the Volute Shape of a Centrifugal Compressor
Directory of Open Access Journals (Sweden)
Martin Heinrich
2016-01-01
Full Text Available A numerical model for the genetic optimization of the volute of a centrifugal compressor for light commercial vehicles is presented. The volute cross-sectional shape is represented by cubic B-splines and its control points are used as design variables. The goal of the global optimization is to maximize the average compressor isentropic efficiency and total pressure ratio at design speed and four operating points. The numerical model consists of a density-based solver in combination with the SST k-ω turbulence model with rotation/curvature correction and the multiple reference frame approach. The initial validation shows a good agreement between the numerical model and test bench measurements. As a result of the optimization, the average total pressure rise and efficiency are increased by over 1.0% compared to the initial designs of the optimization, while the maximum efficiency rise is nearly 2.5% at m˙corr=0.19 kg/s.
Shape optimization of a sheet swimming over a thin liquid layer
Energy Technology Data Exchange (ETDEWEB)
Wilkening, J.; Hosoi, A.E.
2008-12-10
Motivated by the propulsion mechanisms adopted by gastropods, annelids and other invertebrates, we consider shape optimization of a flexible sheet that moves by propagating deformation waves along its body. The self-propelled sheet is separated from a rigid substrate by a thin layer of viscous Newtonian fluid. We use a lubrication approximation to model the dynamics and derive the relevant Euler-Lagrange equations to simultaneously optimize swimming speed, efficiency and fluid loss. We find that as the parameters controlling these quantities approach critical values, the optimal solutions become singular in a self-similar fashion and sometimes leave the realm of validity of the lubrication model. We explore these singular limits by computing higher order corrections to the zeroth order theory and find that wave profiles that develop cusp-like singularities are appropriately penalized, yielding non-singular optimal solutions. These corrections are themselves validated by comparison with finite element solutions of the full Stokes equations, and, to the extent possible, using recent rigorous a-priori error bounds.
Directory of Open Access Journals (Sweden)
Yang Fan
2012-10-01
Full Text Available Abstract Background Computer-assisted surgical navigation aims to provide surgeons with anatomical target localization and critical structure observation, where medical image processing methods such as segmentation, registration and visualization play a critical role. Percutaneous renal intervention plays an important role in several minimally-invasive surgeries of kidney, such as Percutaneous Nephrolithotomy (PCNL and Radio-Frequency Ablation (RFA of kidney tumors, which refers to a surgical procedure where access to a target inside the kidney by a needle puncture of the skin. Thus, kidney segmentation is a key step in developing any ultrasound-based computer-aided diagnosis systems for percutaneous renal intervention. Methods In this paper, we proposed a novel framework for kidney segmentation of ultrasound (US images combined with nonlocal total variation (NLTV image denoising, distance regularized level set evolution (DRLSE and shape prior. Firstly, a denoised US image was obtained by NLTV image denoising. Secondly, DRLSE was applied in the kidney segmentation to get binary image. In this case, black and white region represented the kidney and the background respectively. The last stage is that the shape prior was applied to get a shape with the smooth boundary from the kidney shape space, which was used to optimize the segmentation result of the second step. The alignment model was used occasionally to enlarge the shape space in order to increase segmentation accuracy. Experimental results on both synthetic images and US data are given to demonstrate the effectiveness and accuracy of the proposed algorithm. Results We applied our segmentation framework on synthetic and real US images to demonstrate the better segmentation results of our method. From the qualitative results, the experiment results show that the segmentation results are much closer to the manual segmentations. The sensitivity (SN, specificity (SP and positive predictive value
十级高压压气机气动方案设计的优化%Aerodynamic Preliminary Design Optimization of Ten-stage High Pressure Compressor
Institute of Scientific and Technical Information of China (English)
斯夏依; 钟勇健; 滕金芳; 刘程远; 羌晓青
2016-01-01
对 HARIKA 程序进行改进，创新性地修正了效率模型并引入 Koch 失速静压升系数模型，采用 E3十级高压压气机气动特性试验数据验证此改进 HARIKA 程序，结果表明改进 HARIKA 程序对压气机100％转速失速边界的预估精度达到了99％。采用 NSGA －II 多目标遗传算法进行气动方案设计优化，优化后的方案与初始方案相比设计点的总效率提高了3．4％，喘振裕度提高了6％；通过调节进口导叶和前五级静子叶片的安装角，使得优化方案在非设计转速下的特性也得到了提高。%The efficiency models Firstly,was improved based on the HARIKA program.The stalling pressure rise method pro-posed by C.C.Koch was used to predict stall margin of axial flow compressors.Then,the modified program was applied to cal-culate the characteristic of a ten-stage compressor.The results show that the accuracy of predicting stall margin achieves 99%. Finally,the NSGA-II was used to optimize the overall aerodynamic design.After optimization,the compressor peak efficiency at the design rotational speed increase by 3.4% compared to the initial characters and its surge margin increase from 1 1.6% to 17.6%.The off-design performances also increase by optimizing the angles of both the inlet guide vanes and the former five vanes.The character lines of 90% design rotational speed shows a higher peak efficiency and surge margin after optimization the stator value.
Arterial cannula shape optimization by means of the rotational firefly algorithm
Tesch, K.; Kaczorowska, K.
2016-03-01
This article presents global optimization results of arterial cannula shapes by means of the newly modified firefly algorithm. The search for the optimal arterial cannula shape is necessary in order to minimize losses and prepare the flow that leaves the circulatory support system of a ventricle (i.e. blood pump) before it reaches the heart. A modification of the standard firefly algorithm, the so-called rotational firefly algorithm, is introduced. It is shown that the rotational firefly algorithm allows for better exploration of search spaces which results in faster convergence and better solutions in comparison with its standard version. This is particularly pronounced for smaller population sizes. Furthermore, it maintains greater diversity of populations for a longer time. A small population size and a low number of iterations are necessary to keep to a minimum the computational cost of the objective function of the problem, which comes from numerical solution of the nonlinear partial differential equations. Moreover, both versions of the firefly algorithm are compared to the state of the art, namely the differential evolution and covariance matrix adaptation evolution strategies.
Topology and shape optimization of induced-charge electro-osmotic micropumps
Energy Technology Data Exchange (ETDEWEB)
Gregersen, M M; Okkels, F; Bruus, H [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Building 345 East, DK-2800 Kongens Lyngby (Denmark); Bazant, M Z [Departments of Chemical Engineering and Mathematics, MIT, Cambridge, MA 02139 (United States)], E-mail: Henrik.Bruus@nanotech.dtu.dk
2009-07-15
For a dielectric solid surrounded by an electrolyte and positioned inside an externally biased parallel-plate capacitor, we study numerically how the resulting induced-charge electro-osmotic (ICEO) flow depends on the topology and shape of the dielectric solid. In particular, we extend existing conventional electrokinetic models with an artificial design field to describe the transition from the liquid electrolyte to the solid dielectric. Using this design field, we have succeeded in applying the method of topology optimization to find system geometries with non-trivial topologies that maximize the net induced electro-osmotic flow rate through the electrolytic capacitor in the direction parallel to the capacitor plates. Once found, the performance of the topology-optimized geometries has been validated by transferring them to conventional electrokinetic models not relying on the artificial design field. Our results show the importance of the topology and shape of the dielectric solid in ICEO systems and point to new designs of ICEO micropumps with significantly improved performance.
OPTIMIZING THE SHAPE OF ROTOR BLADES FOR MAXIMUM POWER EXTRACTION IN MARINE CURRENT TURBINES
Directory of Open Access Journals (Sweden)
J.A. Esfahani
2012-12-01
Full Text Available In this paper the shape of rotor blades in Marine Current Turbines (MCTs are investigated. The evaluation of hydrodynamic loads on blades is performed based on the Blade Element Momentum (BEM theory. The shape of blades is optimized according to the main parameters in the configuration and operation of these devices. The optimization is conducted based on the ability of the blades to harness the maximum energy during operating. The main parameters investigated are the tip speed ratio and angle of attack. Furthermore, the influence of these parameters on the maximum energy extraction from fluid flow over a hydrofoil is evaluated. It is shown that the effect of the angle of attack on power extraction is greater than that of the tip speed ratio, while both are found to be significant. Additionally, the proper angle of attack is the angle at which the lift to drag ratio is at its maximum value. However, if a proper angle of attack is chosen, the variations in power coefficient would not be effectively changed with small variations in the tip speed ratio.
Chumachenko, E. N.
2008-08-01
The necessity to develop and optimize new technological processes of gas moulding of shells under the superplasticity conditions, which ensure large elongation and complexity of the shape of end items, makes the specialists in the field of mathematical simulation to pose and solve problems of constant improvement of the imitation models. Because of a large number of "embedded" nonlinearities (the physical properties of the material, friction, and unknown boundaries), the solution of such problems requires large computer resources, high qualification of designers, and large amount of labor. In the present paper, we consider the problems of express analysis of pattern change of spatial shells on the basis of estimation of the behavior of their critical cross-sections. We solve problems of moulding of titan shells (made of VT6 alloy) in a matrix of complicated shape. We theoretically and experimentally justify the methods for predicting and constructing the optimal technological processes of shell deformation under conditions close to superplasticity by using the 2.5D designing procedures.
Institute of Scientific and Technical Information of China (English)
王永志; 张卫民; 康传明; 岳良明
2012-01-01
An aerodynamics/structure integrated design method of composite blade of wind turbine was presented based on multidisciplinary design optimization. Multi-island Genetic Algorithm was used to optimize the mass of composite blade with constrains of aerodynamic and structural performance. A blade element momentum theory ( BEM) method was used in aerodynamic analysis considering tip loss and hub loss. 3D parametric CAD model was analyzed with finite element method (FEM). The results show that the method brings higher efficiency.%基于多学科优化理论,提出复合材料风力机叶片气动/结构一体化优化设计方法.采用多岛遗传算法,以叶片的气动和结构性能为约束、质量为目标,对复合材料风力机叶片进行优化设计.气动性能分析采用叶素动量理论,考虑叶梢损失和轮毂损失.结构分析采用有限元方法对风机叶片三维参数化CAD模型进行分析.算例结果证明了该方法的有效性,对实际的工程设计有较强的参考价值.
Institute of Scientific and Technical Information of China (English)
王骑; 廖海黎; 李明水; 马存明
2012-01-01
Taken a streamline box girder for example, the influence of aerodynamic shape on bridge flutter and vertex-induced vibration ( VIV) was studied in detail. Through wind tunnel test of a 1: 50 scale section model, the influences of railing, inspection rail, rostrum, guide wing and inclined web on the flutter and VIV were discussed respectively. The results indicate that railing and inspection rail could weaken the aerodynamic performance of bridge section, while rostrum and guide wing could be used to improve the flutter and VIV performance of bridge. Special indicating is that the increase of flutter wind speed and the vanishing of VIV were all satisfied under the same condition while the slope of inclined web was 15° The brief mechanism of this phenomenon is that the lower inclined web could restrain and delay the formation and shedding of the vertex at the downwind of streamline box girder, thus could remarkably weaken the influence of vertex shedding on VIV and flutter of bridges. But the detailed aerodynamic mechanism will be studied profoundly in future. This development would be beneficial to the wind resistant design of the bridge, and has been applied successfully in the aerodynamic shape design of several long-span bridges in China.%以某流线型钢箱梁断面为例,详细研究了主梁气动外形变化对桥梁颤振和涡振性能的影响.基于1∶50节段模型风洞试验,分别研究了箱梁的栏杆、检修车轨道、风嘴、导流板,以及斜腹板对桥梁颤振及涡振性能的影响.研究表明,栏杆和检修车轨道将弱化桥梁断面的气动性能,而风嘴和导流板则对桥梁的颤振和涡振性能有利.值得提出的是,在其他气动外形保持不变,而斜腹板倾角变为15°时,桥梁的颤振性能不仅获得了较大提升,且涡振现象还可得到消除.此现象的初步机理为:较小的斜腹板倾角可阻碍和廷后流线型箱梁下风侧漩涡的形成和脱落,从而显著削弱漩涡脱
Institute of Scientific and Technical Information of China (English)
车刚; 徐通模; 许卫疆; 惠世恩
2001-01-01
A study on a cold-state model of aerodynamic characteristics was conducted of a W-shaped flame boiler equipped with a direct-flow slit type burner. The 360 MW boiler is a product of French Stein Co. With the help of a hot-wire anemometer the velocity distribution of a flow field in the furnace was measured and the flow field diagram of W-shaped air flow in the furnace under various operating conditions obtained. An analysis has been performed with respect to the following: the law of air flow velocity distribution of the flow field under different operating regimes, the filling fullness of air within the furnace, the air flow path, velocity excursions at the furnace outlet, etc. Also studied are the in-furnace aerodynamic field characteristics and their variation law and mechanism along with a measurement of flame short circuiting of the W-shaped flame boiler and the velocity excursions at the furnace outlet%针对引进的配备直流缝隙式燃烧器的法国Stein公司360 MW的W型火焰锅炉进行了冷态模型的空气动力特性研究。利用热线风速仪测量炉内的流场速度，得出了不同工况下炉内W型气流的流场图，并对不同工况流场的气流速度分布规律、炉内气流的充满度、气流行程、炉膛出口处的速度偏差等进行了分析，研究了炉内空气动力场的特性和变化规律，测试了W型火焰锅炉火焰短路与炉膛出口速度偏差的性能。
Optimal blade shape of a modified Savonius turbine using an obstacle shielding the returning blade
Energy Technology Data Exchange (ETDEWEB)
Mohamed, M.H.; Janiga, G.; Pap, E.; Thevenin, D. [Lab. of Fluid Dynamics and Technical Flows, University of Magdeburg ' ' Otto von Guericke' ' (Germany)
2011-01-15
Due to the worldwide energy crisis, research and development activities in the field of renewable energy have been considerably increased in many countries. Wind energy is becoming particularly important. Although considerable progress have already been achieved, the available technical design is not yet adequate to develop reliable wind energy converters for conditions corresponding to low wind speeds and urban areas. The Savonius turbine appears to be particularly promising for such conditions, but suffers from a poor efficiency. The present study considers a considerably improved design in order to increase the output power of a classical Savonius turbine. In previous works, the efficiency of the classical Savonius turbine has been increased by placing in an optimal manner an obstacle plate shielding the returning blade. The present study now aims at improving further the output power of the Savonius turbine as well as the static torque, which measures the self-starting capability of the turbine. In order to achieve both objectives, the geometry of the blade shape (skeleton line) is now optimized in presence of the obstacle plate. Six free parameters are considered in this optimization process, realized by coupling an in-house optimization library (OPAL, relying in the present case on Evolutionary Algorithms) with an industrial flow simulation code (ANSYS-Fluent). The target function is the output power coefficient. Compared to a standard Savonius turbine, a relative increase of the power output coefficient by almost 40% is finally obtained at {lambda} = 0.7. The performance increase exceeds 30% throughout the useful operating range. Finally, the static torque is investigated and found to be positive at any angle, high enough to obtain self-starting conditions. (author)
Shape Optimization of Hollow Concrete Blocks Using the Lattice Discrete Particle Model
Directory of Open Access Journals (Sweden)
Fatemeh Javidan
2013-01-01
Full Text Available Hollow concrete blocks are one of the widely used building elements of masonry structures in whichthey are normally loaded under combined action of shear and compression. Accordingly and due to theirstructural importance, the present study intends to numerically search for an optimum shape of such blocks.The optimality index is selected to be the ratio of block’s failure strength to its weight, a non-dimensionalparameter, which needs to be maximized. The nonlinear analysis has been done using a homemade code writtenbased on the recently developed Lattice Discrete Particle Model (LDPM for the meso-scale simulation ofconcrete. This numerical approach accounts for the different aspects of concrete’s complex behavior such astensile fracturing, cohesive and frictional shearing and also its nonlinear compressive response. The modelparameters were calibrated against previously reported experimental data. Various two-core configurations forthe hollow blocks are examined, compared and discussed.
Solving time-dependent problems by an RBF-PS method with an optimal shape parameter
Energy Technology Data Exchange (ETDEWEB)
Neves, A M A; Roque, C M C; Ferreira, A J M; Jorge, R M N [Departamento de Engenharia Mecanica e Gestao Industrial, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Soares, C M M, E-mail: ana.m.neves@fe.up.p, E-mail: croque@fe.up.p, E-mail: ferreira@fe.up.p, E-mail: cristovao.mota.soares@dem.ist.utl.p, E-mail: rnatal@fe.up.p [IDMEC - Instituto de Engenharia Mecanica - Instituto Superior Tecnico, Av. Rovisco Pais, 1096 Lisboa Codex (Portugal)
2009-08-01
An hybrid technique is used for the solutions of static and time-dependent problems. The idea is to combine the radial basis function (RBF) collocation method and the pseudospectal (PS) method getting to the RBF-PS method. The approach presented in this paper includes a shape parameter optimization and produces highly accurate results. Different examples of the procedure are presented and different radial basis functions are used. One and two-dimensional problems are considered with various boundary and initial conditions. We consider generic problems, but also results on beams and plates. The displacement and the stress analysis are conducted for static and transient dynamic situations. Results obtained are in good agreement with exact solutions or references considered.
Directory of Open Access Journals (Sweden)
Guoqiang You
2015-01-01
Full Text Available Based on structural features of cable-net of deployable antenna, a multiobjective shape optimization method is proposed to help to engineer antenna’s cable-net structure that has better deployment and adjustment properties. In this method, the multiobjective optimum mathematical model is built with lower nodes’ locations of cable-net as variables, the average stress ratio of cable elements and strain energy as objectives, and surface precision and natural frequency of cable-net as constraints. Sequential quadratic programming method is used to solve this nonlinear mathematical model in conditions with different weighting coefficients, and the results show the validity and effectiveness of the proposed method and model.
Energy Technology Data Exchange (ETDEWEB)
Jiang, Shaoen; Ding, Yongkun [Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Huang, Yunbao, E-mail: Huangyblhy@gmail.com, E-mail: scmyking-2008@163.com; Li, Haiyan [Key Laboratory of Computer Integrated Manufacturing System, Guangdong University of Technology, Guangzhou 510006 (China); Jing, Longfei, E-mail: Huangyblhy@gmail.com, E-mail: scmyking-2008@163.com; Huang, Tianxuan [Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900 (China)
2016-01-15
The hohlraum is very crucial for indirect laser driven Inertial Confinement Fusion. Usually, its shape is designed as sphere, cylinder, or rugby with some kind of fixed functions, such as ellipse or parabola. Recently, a spherical hohlraum with octahedral 6 laser entrance holes (LEHs) has been presented with high flux symmetry [Lan et al., Phys. Plasmas 21, 010704 (2014); 21, 052704 (2014)]. However, there is only one shape parameter, i.e., the hohlraum to capsule radius ratio, being optimized. In this paper, we build the hohlraum with octahedral 6LEHs with a unified free-form representation, in which, by varying additional shape parameters: (1) available hohlraum shapes can be uniformly and accurately represented, (2) it can be used to understand why the spherical hohlraum has higher flux symmetry, (3) it allows us to obtain a feasible shape design field satisfying flux symmetry constraints, and (4) a synthetically optimized hohlraum can be obtained with a tradeoff of flux symmetry and other hohlraum performance. Finally, the hohlraum with octahedral 6LEHs is modeled, analyzed, and then optimized based on the unified free-form representation. The results show that a feasible shape design field with flux asymmetry no more than 1% can be obtained, and over the feasible design field, the spherical hohlraum is validated to have the highest flux symmetry, and a synthetically optimal hohlraum can be found with closing flux symmetry but larger volume between laser spots and centrally located capsule.
Optimization of a T-shaped optical grating for specific applications
Szarvas, Tamás; Kis, Zsolt
2016-07-01
A detailed analysis of the optical reflectivity of a monolithic, T-shaped surface relief grating structure is carried out. It is shown that by changing the groove depths and widths, the frequency-dependent reflectivity of the diffraction grating can be greatly modified to obtain various specific optical elements. The basic T-shaped grating structure is optimized for three specific applications: a perfect mirror with a wide maximal reflection plateau, a bandpass filter, and a dichroic beam splitter. These specific mirrors could be used to steer the propagation of bichromatic laser fields, in situations where multilayer dielectric mirrors cannot be applied due to their worse thermomechanical properties. Colored maps are presented to show the reflection dependency on the variation of several critical structure parameters. To check the accuracy of the numerical results, four independent methods are used: finite-difference time-domain, finite-difference frequency-domain, method of lines, and rigorous coupled-wave analysis. The results of the independent numerical methods agree very well with each other indicating their correctness.
Interpolation of longitudinal shape and image data via optimal mass transport
Gao, Yi; Zhu, Liang-Jia; Bouix, Sylvain; Tannenbaum, Allen
2014-03-01
Longitudinal analysis of medical imaging data has become central to the study of many disorders. Unfortunately, various constraints (study design, patient availability, technological limitations) restrict the acquisition of data to only a few time points, limiting the study of continuous disease/treatment progression. Having the ability to produce a sensible time interpolation of the data can lead to improved analysis, such as intuitive visualizations of anatomical changes, or the creation of more samples to improve statistical analysis. In this work, we model interpolation of medical image data, in particular shape data, using the theory of optimal mass transport (OMT), which can construct a continuous transition from two time points while preserving "mass" (e.g., image intensity, shape volume) during the transition. The theory even allows a short extrapolation in time and may help predict short-term treatment impact or disease progression on anatomical structure. We apply the proposed method to the hippocampus-amygdala complex in schizophrenia, the heart in atrial fibrillation, and full head MR images in traumatic brain injury.
Constellation Shaping for WDM systems using 256QAM/1024QAM with Probabilistic Optimization
Yankov, Metodi P; da Silva, Edson P; Forchhammer, Søren; Larsen, Knud J; Oxenløwe, Leif K; Galili, Michael; Zibar, Darko
2016-01-01
In this paper, probabilistic shaping is numerically and experimentally investigated for increasing the transmission reach of wavelength division multiplexed (WDM) optical communication system employing quadrature amplitude modulation (QAM). An optimized probability mass function (PMF) of the QAM symbols is first found from a modified Blahut-Arimoto algorithm for the optical channel. A turbo coded bit interleaved coded modulation system is then applied, which relies on many-to-one labeling to achieve the desired PMF, thereby achieving shaping gain. Pilot symbols at rate at most 2% are used for synchronization and equalization, making it possible to receive input constellations as large as 1024QAM. The system is evaluated experimentally on a 10 GBaud, 5 channels WDM setup. The maximum system reach is increased w.r.t. standard 1024QAM by 20% at input data rate of 4.65 bits/symbol and up to 75% at 5.46 bits/symbol. It is shown that rate adaptation does not require changing of the modulation format. The performanc...
Advanced Topics in Aerodynamics
DEFF Research Database (Denmark)
Filippone, Antonino
1999-01-01
"Advanced Topics in Aerodynamics" is a comprehensive electronic guide to aerodynamics,computational fluid dynamics, aeronautics, aerospace propulsion systems, design and relatedtechnology. We report data, tables, graphics, sketches,examples, results, photos, technical andscientific literature...
Feasible optimal deformable mirror shaping algorithm for high-contrast imaging
Give'on, Amir; Kasdin, N. Jeremy; Vanderbei, Robert J.; Spergel, David N.; Littman, Michael G.; Gurfil, Pini
2003-12-01
The Princeton University Terrestrial Planet Finder (TPF) group has been working on a novel method for direct imaging of extra solar planets using a shaped-pupil coronagraph. The entrance pupil of the coronagraph is optimized to have a point spread function (PSF) that provides the suppression level needed at the angular separation required for detection of extra solar planets. When integration time is to be minimized, the photon count at the planet location in the image plane is a Poisson distributed random process. The ultimate limitation of these high-dynamic-range imaging systems comes from scattering due to imperfections in the optical surfaces of the collecting system. The first step in correcting the wavefront errors is the estimation of the phase aberrations. The phase aberration caused by these imperfections is assumed to be a sum of two-dimensional sinusoidal functions. Assuming one uses a deformable mirror to correct these aberrations, we propose an algorithm that optimally decreases the scattering level in specified localized areas in the image plane independent of the choice of influence function of the deformable mirror.
Application of software for the optimization of the surface shape of nets for chestnut harvesting
Directory of Open Access Journals (Sweden)
Andrea Formato
2013-09-01
Full Text Available In this research conveyance nets for the chestnuts harvest have been considered and the optimization of the surface shape of the chestnuts harvest nets has been performed. Indeed, a steep zone with chestnut trees has been considered, with maximum length of 90 m and maximum width of 60 m and the geometric model of the considered zone has been obtained, by mean GIS system and “Archicad 14” program code, obtaining also the soil local slope distribution. The chestnuts fallen have been simulated by mean a “rain device” available in “Sitetopo” program code. This program has allowed to evaluate the rain draining in function of the considered surface slope. Further, the zone with lower quote, for the considered surface, is the zone in that the chestnuts have to be convoyed, “basin zone”. Indeed, by mean “Sitetopo” program code, it has been possible to evaluate the rain draining contour-plot, and the conveyance effect, that is, where the rain flow is convoyed. This has been obtained by changing of the net surface slope on that, the rain (simulating the chestnuts fallen. Indeed the nets have been located following the determined optimal surface. In such way all the fallen chestnuts have been convoyed and picked in a determined zone, “basin zone”, and subsequently they have been loaded on the truck for the following workmanships. The evaluated losses have been of around 6-8 % due to chestnuts entangle or little branches obstacle.
Reich, Daniel M
2013-01-01
Laser cooling of molecules employing broadband optical pumping involves a timescale separation between laser excitation and spontaneous emission. Here, we optimize the optical pumping step using shaped laser pulses. We derive two optimization functionals to drive population into those excited state levels that have the largest spontaneous emission rates to the target state. We show that, when using optimal control, laser cooling of molecules works even if the Franck-Condon map governing the transitions is preferential to heating rather than cooling. Our optimization functional is also applicable to the laser cooling of other degrees of freedom provided the cooling cycle consists of coherent excitation and dissipative deexcitation steps whose timescales are separated.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The squirrel-cage elastic support is one of the most important components of an aero-engine rotor system.A proper structural design will favor the static and dynamic performances of the system.In view of the deficiency of the current shape optimization techniques,a new mapping approach is proposed to define shape design variables based on the parametric equations of 3D curves and surfaces.It is then applied for the slot shape optimization of a squirrel-cage elastic support.To this end,an automatic design procedure that integrates the Genetic Algorithm (GA) is developed to solve the problem.Two typical examples with different shape constraints are considered.Numerical results provide reasonable optimum designs for the improvement of stiffness and strength of the squirrel-cage elastic support.
Institute of Scientific and Technical Information of China (English)
赵磊; 乔渭阳; 谭洪川
2013-01-01
The low pressure turbine of an aircraft is an important engine noise source at approach power, and there is a high requirement on its aerodynamic efficiency. The noise level of a low pressure turbine must be considered together with its aerodynamic performance to achieve a significantly quiet low pressure turbine design. In this paper some insights are presented on three-dimensional aerodynamic-acousitc optimization for a high performance and low noise level turbine. First, a steady computational fluid dynamics (CFD) simulation is made to evaluate the aerodynamic performance with three-dimensional design variations. Then the unsteady aerodynamic effects and tonal noise level are obtained using unsteady CFD calculation combined with a triple-plane pressure (TPP) matching strategy. Finally an optimal design plan is selected. Taking as an example the calculation of the last stage of a GE-E3 (Energy Efficient Engine) low pressure turbine, the potential of using lean vanes as a turbine tonal noise reduction strategy is numerically simulated. The results show that when the positive lean angle is smaller than 19° the single stage turbine performance is improved, with a maximum enhancement of efficiency of 0. 3% . Evaluation of tonal noise shows that positive lean increases the noise level, for it changes the characteristics of vane wakes, which means this method cannot be employed for noise reduction. The numerical simulation indicates that this three-dimensional optimization method can reflect simultaneously the effects of detailed three-dimensional changes of a blade on its aerodynamic and acoustic performance, and it can be effectively used in the aerodynamic-acousitc optimization process.%低压涡轮既是飞机进场着陆时发动机的重要声源,也是发动机中对效率要求很高的部件之一,为了实现低压涡轮低噪声的设计目标必须同时兼顾气动性能指标.研究给出了高效低噪声低压涡轮气动-声学三维优化的思路,
Luo, Xiangyou; Yang, Bo; Sheng, Lei; Chen, Jinlong; Li, Hui; Xie, Li; Chen, Gang; Yu, Mei; Guo, Weihua; Tian, Weidong
2015-07-01
Tooth root supports dental crown and bears occlusal force. While proper root shape and size render the force being evenly delivered and dispersed into jawbone. Yet it remains unclear what shape and size of a biological tooth root (bio-root), which is mostly determined by the scaffold geometric design, is suitable for stress distributing and mastication performing. Therefore, this study hypothesized scaffold fabricated in proper shape and size is better for regeneration of tooth root with approving biomechanical functional features. In this study, we optimized shape and size of scaffolds for bio-root regeneration using computer aided design (CAD) modeling and finite element analysis (FEA). Statical structural analysis showed the total deformation (TD) and equivalent von-mises stress (EQV) of the restored tooth model mainly concentrated on the scaffold and the post, in accordance with the condition in a natural post restored tooth. Design sensitivity analysis showed increasing the height and upper diameter of the scaffold can tremendously reduce the TD and EQV of the model, while increasing the bottom diameter of scaffold can, to some extent, reduce the EQV in post. However, increase on post height had little influence on the whole model, only slightly increased the native EQV stress in post. Through response surface based optimization, we successfully screened out the optimal shape of the scaffold used in tissue engineering of tooth root. The optimal scaffold adopted a slightly tapered shape with the upper diameter of 4.9 mm, bottom diameter of 3.4 mm; the length of the optimized scaffold shape was 9.4 mm. While the analysis also suggested a height of about 9 mm for a metal post with a diameter of 1.4 mm suitable for crown restoration in bio-root regeneration. In order to validate the physiological function of the shape optimized scaffold in vivo, we transplanted the shape optimized treated dentin matrix (TDM) scaffold, seeding with dental stem cells, into alveolar
某车型A柱风噪优化研究%Study on Aerodynamic Noise Optimization for a Vehicle A-pillar
Institute of Scientific and Technical Information of China (English)
王俊; 龚旭; 张涛; 陈如意
2015-01-01
Investigation is made to a Chinese brand vehicle which has awful aerodynamic noise in cross wind environment, it is found that A-pillar design defect makes it a noise source in cross wind. It is identified based on CFD analysis method that airflow separation zone is markedly decreased by installing A-pillar garnish and modifying the A-pillar surface. Then the optimization of adding A-pillar garnish has been tested in wind tunnel, which includes the SPL (sound pressure level) test on the side window surface and in the passenger cabinet, the results show that the average SPL of test point on side window surface and the speech intelligibility index in passenger cabinet have a distinct improvement. Finally the design key points and noise improvement measures for A-pillar is summarized, the crosswind flow field analysis for A-pillar is necessary in car body design process.%针对某自主车型侧风下出现风噪较大的问题，查找原因发现A柱设计缺陷使其在侧风下成为一个显著的噪声源。基于CFD分析方法发现，通过增加A柱装饰件和修改A柱型面，均能明显减小气流分离区。在风洞中对增加A柱装饰件的优化方案进行了由车外至车内的风噪测试，测试结果表明，该方案对侧窗表面声压级和语言清晰度有明显的优化效果。总结出A柱的设计要点及风噪的改善措施，指出在车身开发过程中必须对A柱进行侧风稳态分析。
AB-BNCT beam shaping assembly based on {sup 7}Li(p,n){sup 7}Be reaction optimization
Energy Technology Data Exchange (ETDEWEB)
Minsky, D.M., E-mail: minsky@tandar.cnea.gov.ar [Gerencia de Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499 (B1650KNA), San Martin, Buenos Aires (Argentina)] [Escuela de Ciencia y Tecnologia, UNSAM, M. de Irigoyen 3100 (1650), San Martin (Argentina)] [CONICET, Av. Rivadavia 1917 (C1033AAJ), Buenos Aires (Argentina); Kreiner, A.J. [Gerencia de Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499 (B1650KNA), San Martin, Buenos Aires (Argentina)] [Escuela de Ciencia y Tecnologia, UNSAM, M. de Irigoyen 3100 (1650), San Martin (Argentina)] [CONICET, Av. Rivadavia 1917 (C1033AAJ), Buenos Aires (Argentina); Valda, A.A. [Gerencia de Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499 (B1650KNA), San Martin, Buenos Aires (Argentina)] [Escuela de Ciencia y Tecnologia, UNSAM, M. de Irigoyen 3100 (1650), San Martin (Argentina)
2011-12-15
A numerical optimization of a Beam Shaping Assembly (BSA) for Accelerator Based-Boron Neutron Capture Therapy (AB-BNCT) has been performed. The reaction {sup 7}Li(p,n){sup 7}Be has been considered using a proton beam on a lithium fluoride target. Proton energy and the dimensions of a simple BSA geometry have been varied to obtain a set of different configurations. The optimal configuration of this set is shown.
Influence of anisotropic piezoelectric actuators on wing aerodynamic forces
Institute of Scientific and Technical Information of China (English)
2008-01-01
Changing the shape of an airfoil to enhance overall aircraft performance has always been a goal of aircraft designers. Using smart material to reshape the wing can improve aerodynamic performance. The influence of anisotropic effects of piezoelectric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated. Test verification was conducted.
Influence of anisotropic piezoelectric actuators on wing aerodynamic forces
Institute of Scientific and Technical Information of China (English)
GUAN De; LI Min; LI Wei; WANG MingChun
2008-01-01
Changing the shape of an airfoil to enhance overall aircraft performance has always been s goal of aircraft designers.Using smart material to reshape the wing can improve aerodynamic performance.The influence of anisotropic effects of piezo-electric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated.Test verification was conducted.
Vasilyev, Oleg V.; Gazzola, Mattia; Koumoutsakos, Petros
2010-11-01
In this talk we discuss preliminary results for the use of hybrid wavelet collocation - Brinkman penalization approach for shape optimization for drag reduction in flows past linked bodies. This optimization relies on Adaptive Wavelet Collocation Method along with the Brinkman penalization technique and the Covariance Matrix Adaptation Evolution Strategy (CMA-ES). Adaptive wavelet collocation method tackles the problem of efficiently resolving a fluid flow on a dynamically adaptive computational grid, while a level set approach is used to describe the body shape and the Brinkman volume penalization allows for an easy variation of flow geometry without requiring body-fitted meshes. We perform 2D simulations of linked bodies in order to investigate whether flat geometries are optimal for drag reduction. In order to accelerate the costly cost function evaluations we exploit the inherent parallelism of ES and we extend the CMA-ES implementation to a multi-host framework. This framework allows for an easy distribution of the cost function evaluations across several parallel architectures and it is not limited to only one computing facility. The resulting optimal shapes are geometrically consistent with the shapes that have been obtained in the pioneering wind tunnel experiments for drag reduction using Evolution Strategies by Ingo Rechenberg.
Salehi, M.; Hamedi, M.; Salmani Nohouji, H.; Arghavani, J.
2014-02-01
Microactuators are essential elements of MEMS and are widely used in these devices. Microgrippers, micropositioners, microfixtures, micropumps and microvalves are well-known applications of microstructures. In this paper, the design optimization of shape memory alloy microactuators is discussed. Four different configurations of microactuator with variable geometrical parameters, generating different levels of displacement and force, are designed and analysed. In order to determine the optimum values of parameters for each microactuator, statistical design of experiments (DOE) is used. For this purpose, the Souza et al constitutive model (1988 Eur. J. Mech. A 17 789-806) is adapted for use in finite element analysis software. Mechanical properties of the SMA are identified by performing experimental tests on Ti-49.8%Ni. Finally, the specific energy of each microactuator is determined using the calibrated model and regression analysis. Moreover, the characteristic curve of each microactuator is obtained and with this virtual tool one can choose a microactuator with the desired force and displacement. The methodology discussed in this paper can be used as a reference to design appropriate microactuators for different MEMS applications producing various ranges of displacement and force.
An optimized neutron-beam shaping assembly for accelerator-based BNCT.
Burlon, A A; Kreiner, A J; Valda, A A; Minsky, D M
2004-11-01
Different materials and proton beam energies have been studied in order to search for an optimized neutron production target and beam shaping assembly for accelerator-based BNCT. The solution proposed in this work consists of successive stacks of Al, polytetrafluoroethylene, commercially known as Teflon, and LiF as moderator and neutron absorber, and Pb as reflector. This assembly is easy to build and its cost is relatively low. An exhaustive Monte Carlo simulation study has been performed evaluating the doses delivered to a Snyder model head phantom by a neutron production Li-metal target based on the (7)Li(p,n)(7)Be reaction for proton bombarding energies of 1.92, 2.0, 2.3 and 2.5 MeV. Three moderator thicknesses have been studied and the figures of merit show the advantage of irradiating with near-resonance-energy protons (2.3 MeV) because of the relatively high neutron yield at this energy, which at the same time keeps the fast neutron healthy tissue dose limited and leads to the lowest treatment times. A moderator of 34 cm length has shown the best performance among the studied cases.
An optimized neutron-beam shaping assembly for accelerator-based BNCT
Energy Technology Data Exchange (ETDEWEB)
Burlon, A.A. E-mail: burlon@tandar.cnea.gov.ar; Kreiner, A.J.; Valda, A.A.; Minsky, D.M
2004-11-01
Different materials and proton beam energies have been studied in order to search for an optimized neutron production target and beam shaping assembly for accelerator-based BNCT. The solution proposed in this work consists of successive stacks of Al, polytetrafluoroethylene, commercially known as Teflon[reg ], and LiF as moderator and neutron absorber, and Pb as reflector. This assembly is easy to build and its cost is relatively low. An exhaustive Monte Carlo simulation study has been performed evaluating the doses delivered to a Snyder model head phantom by a neutron production Li-metal target based on the {sup 7}Li(p,n){sup 7}Be reaction for proton bombarding energies of 1.92, 2.0, 2.3 and 2.5 MeV. Three moderator thicknesses have been studied and the figures of merit show the advantage of irradiating with near-resonance-energy protons (2.3 MeV) because of the relatively high neutron yield at this energy, which at the same time keeps the fast neutron healthy tissue dose limited and leads to the lowest treatment times. A moderator of 34 cm length has shown the best performance among the studied cases.
Markowski, Konrad; Jedrzejewski, Kazimierz; Osuch, Tomasz
2016-09-01
This article presents implementation of the Simulated Annealing (SA) algorithm for tapered fiber Bragg gratings (TFBGs) design. Particularly, together with well-known Coupled Mode Theory (CMT) and Transfer Matrix Method (TMM) the algorithm optimizes the group delay response of TFBG, by simultaneous shaping of both apodization function and tapered fiber transition profile. Prior to the optimization process, numerical model for TFBG design has been validated. Preliminary results reveal great potential of the SA-based approach and with proper definition of the design criteria may be even applied for optimization of the spectral properties of TFBGs.
The aerodynamic and structural study of flapping wing vehicles
2013-01-01
This thesis reports on the aerodynamic and structural study carried out on flapping wings and flapping vehicles. Theoretical and experimental investigation of aerodynamic forces acting on flapping wings in simple harmonic oscillations is undertaken in order to help conduct and optimize the aerodynamic and structural design of flapping wing vehicles. The research is focused on the large scale ornithopter design of similar size and configuration to a hang glider. By means of Theodorsen’s th...
Institute of Scientific and Technical Information of China (English)
唐智礼
2006-01-01
将确定性优化算法和Pareto阵面概念结合起来处理了多目标优化设计问题;给出了结合算法及数值过程的细节,并将其应用到了气动优化设计中;描述了如何用确定性优化算法快速抓获多目标优化问题的Pareto阵面以及能够抓获哪些类型的Pareto阵面.数值实验结果表明,确定性优化算法可以准确高效地抓获任意凸的和某些凹的Pareto阵面,故对于此类多目标气动优化问题,可用确定性算法代替进化算法.%Deterministic optimization methods are combined with the Pareto front concept to solve multi-criterion design problems. The algorithm and the numerical implementation are applied to aerodynamic designs. Evolutionary algorithms (EAs) and the Pareto front concept are used to solve practical design problems in industry for its robustness in capturing convex, concave, discrete or discontinuous Pareto fronts of multi-objective optimization problems. However, the process is time-consuming. Therefore, deterministic optimization methods are introduced to capture the Pareto front, and the types of the captured Pareto front are explained. Numerical experiments show that the deterministic optimization method is a good alternative to EAs for capturing any convex and some concave Pareto fronts in multi-criterion aerodynamic optimization problems due to its efficiency.
Fourier analysis of the aerodynamic behavior of cup anemometers
Pindado Carrion, Santiago; Pérez Sarasola, Imanol; Aguado Roca, Maite
2013-01-01
The calibration results (the transfer function) of an anemometer equipped with several cup rotors were analyzed and correlated with the aerodynamic forces measured on the isolated cups in a wind tunnel. The correlation was based on a Fourier analysis of the normal-to-the-cup aerodynamic force. Three different cup shapes were studied: typical conical cups, elliptical cups and porous cups (conical-truncated shape). Results indicated a good correlation between the anemometer factor, K, and the r...
Fourier analysis of the aerodynamic behavior of cup anemometers
Pindado, Santiago; Pérez, Imanol; Aguado, Maite
2013-06-01
The calibration results (the transfer function) of an anemometer equipped with several cup rotors were analyzed and correlated with the aerodynamic forces measured on the isolated cups in a wind tunnel. The correlation was based on a Fourier analysis of the normal-to-the-cup aerodynamic force. Three different cup shapes were studied: typical conical cups, elliptical cups and porous cups (conical-truncated shape). Results indicated a good correlation between the anemometer factor, K, and the ratio between the first two coefficients in the Fourier series decomposition of the normal-to-the-cup aerodynamic force.
Institute of Scientific and Technical Information of China (English)
孙丽玲; 胡静涛; 胡琨元; 何茂伟; 陈瀚宁
2016-01-01
A new multi-species particle swarm optimization with a two-level hierarchical topology and the orthogonal learning strategy (OMSPSO) is proposed, which enhances the global search ability of particles and increases their convergence rates. The numerical results on 10 benchmark functions demonstrated the effectiveness of our proposed algorithm. Then, the proposed algorithm is presented to design a butterfly-shaped microstrip patch antenna. Combined with the HFSS solver, a butterfly-shaped patch antenna with a bandwidth of about 40.1% is designed by using the proposed OMSPSO. The return loss of the butterfly-shaped antenna is greater than 10 dB between 4.15 and 6.36 GHz. The antenna can serve simultaneously for the high-speed wireless computer networks (5.15–5.35 GHz) and the RFID systems (5.8 GHz).
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper,constructal optimization of the twice Y-shaped assemblies of fins with six freedom degrees (characteristic parameters of geometry) is performed by employing finite element method and taking dimensionless maximum thermal resistance as a performance index,and the heat transfer performance of the twice Y-shaped assemblies of fins under various conditions with different freedom degrees are analyzed. The results show that the twice assemblies can improve the heat transfer performance of Y-shaped fin remarkably,and the minimum maximum thermal resistance of the twice Y-shaped assemblies of fins decreases by 36.37% compared with that of once Y-shaped assembly of fins. It is also proved again that the larger the number of freedom degrees for evolving is,the more perfect the system performance is. The effects of different characteristic parameters of geometry on the performance of the twice Y-shaped assemblies of fins are different,one should pay different attention to these parameters in practical engineering designs. The effects of two angles on the maximum thermal resistance are larger,but the optima of the two angles are robust. The effects of two height ratios on the maximum thermal resistance are more remarkable than those of two thickness ratios.
Chen, Junning; Ahmad, Rohana; Suenaga, Hanako; Li, Wei; Sasaki, Keiichi; Swain, Michael; Li, Qing
2015-01-01
With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD), to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE) model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO) technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT), potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM) for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption.
Directory of Open Access Journals (Sweden)
Junning Chen
Full Text Available With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD, to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT, potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption.
2015-01-01
With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD), to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE) model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO) technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT), potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM) for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption. PMID:26161878
Optimization of the Upper Surface of Hypersonic Vehicle Based on CFD Analysis
Gao, T. Y.; Cui, K.; Hu, S. C.; Wang, X. P.; Yang, G. W.
2011-09-01
For the hypersonic vehicle, the aerodynamic performance becomes more intensive. Therefore, it is a significant event to optimize the shape of the hypersonic vehicle to achieve the project demands. It is a key technology to promote the performance of the hypersonic vehicle with the method of shape optimization. Based on the existing vehicle, the optimization to the upper surface of the Simplified hypersonic vehicle was done to obtain a shape which suits the project demand. At the cruising condition, the upper surface was parameterized with the B-Spline curve method. The incremental parametric method and the reconstruction technology of the local mesh were applied here. The whole flow field was been calculated and the aerodynamic performance of the craft were obtained by the computational fluid dynamic (CFD) technology. Then the vehicle shape was optimized to achieve the maximum lift-drag ratio at attack angle 3°, 4° and 5°. The results will provide the reference for the practical design.
Energy Technology Data Exchange (ETDEWEB)
Sharma, Sitansh, E-mail: sitansh@research.iiit.ac.in [Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad 500 032 (India); Singh, Harjinder, E-mail: harjinder.singh@iiit.ac.in [Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad 500 032 (India)
2011-11-18
Graphical abstract: Application of genetic algorithm optimization to control dissociation process in the ground electronic state of HF molecule is demonstrated. Highlights: Black-Right-Pointing-Pointer Genetic algorithm optimization for the design of laser pulses. Black-Right-Pointing-Pointer Control of dissociation process in the ground electronic state of HF molecule. Black-Right-Pointing-Pointer Two types of pulses, one with fixed frequency components and the other having non-deterministic components. Black-Right-Pointing-Pointer Optimized laser fields possess simple time and frequency structures. - Abstract: We have applied genetic algorithm optimization for the design of laser pulses to control dissociation process in the ground electronic state of HF molecule, within the mathematical framework of optimal control theory. In order to design the experimentally feasible laser fields, we coded the small set of selected field parameters in the GA parameter space. Two types of pulses, one with fixed frequency components and the other having non-deterministic components have been designed. Optimized laser field obtained using this approach, possesses simple time and frequency structures. We show that the fields having non-deterministic frequency components lead to greater dissociation probability compared to the ones having deterministic frequency components.
INTEGRATED AERODYNAMIC MEASUREMENTS
SCHUTTE, HK
1992-01-01
The myoelastic-aerodynamic model of phonation implies that aerodynamic factors are crucial to the evaluation of voice function, Subglottal pressure and mean flow rate represent the vocal power source. If they can be related to the magnitude of the radiated sound power, they may provide an index of v
Reinforced aerodynamic profile
DEFF Research Database (Denmark)
2010-01-01
The present invention relates to the prevention of deformations in an aerodynamic profile caused by lack of resistance to the bending moment forces that are created when such a profile is loaded in operation. More specifically, the invention relates to a reinforcing element inside an aerodynamic...
Institute of Scientific and Technical Information of China (English)
Young T. CHAE; Kwang Ho LEE; Jae Sung PARK
2011-01-01
The thermal performance enhancement of the hydronic radiant floor heating system by tube shape refinements is investigated in this paper. Both analytical and detailed numerical modelings are carried out to predict the performance of the radiant system. While the simple analytical model briefly investigates the possibility of the effect of the tube shape improvement with the parametric analysis, the commercial computational fluid dynamics (CFD) code (Ansys/CFX) is used to perform the detailed 3D analysis under different tube shape conditions. The fin thickness, the number of fins, and the tube thermal conductivity turn out to have significant effects on the radiant system performance. The potential energy saving impacts of the tube shape refinements are also discussed. The tube shape improvement turns out to increase the floor surface temperature and to decrease the hot water temperature drop across the system, resulting in heating energy savings.
Application of CAD/CAE class systems to aerodynamic analysis of electric race cars
Grabowski, L.; Baier, A.; Buchacz, A.; Majzner, M.; Sobek, M.
2015-11-01
Aerodynamics is one of the most important factors which influence on every aspect of a design of a car and car driving parameters. The biggest influence aerodynamics has on design of a shape of a race car body, especially when the main objective of the race is the longest distance driven in period of time, which can not be achieved without low energy consumption and low drag of a car. Designing shape of the vehicle body that must generate the lowest possible drag force, without compromising the other parameters of the drive. In the article entitled „Application of CAD/CAE class systems to aerodynamic analysis of electric race cars” are being presented problems solved by computer analysis of cars aerodynamics and free form modelling. Analysis have been subjected to existing race car of a Silesian Greenpower Race Team. On a basis of results of analysis of existence of Kammback aerodynamic effect innovative car body were modeled. Afterwards aerodynamic analysis were performed to verify existence of aerodynamic effect for innovative shape and to recognize aerodynamics parameters of the shape. Analysis results in the values of coefficients and aerodynamic drag forces. The resulting drag forces Fx, drag coefficients Cx(Cd) and aerodynamic factors Cx*A allowed to compare all of the shapes to each other. Pressure distribution, air velocities and streams courses were useful in determining aerodynamic features of analyzed shape. For aerodynamic tests was used Ansys Fluent CFD software. In a paper the ways of surface modeling with usage of Realize Shape module and classic surface modeling were presented. For shapes modeling Siemens NX 9.0 software was used. Obtained results were used to estimation of existing shapes and to make appropriate conclusions.
Energy Technology Data Exchange (ETDEWEB)
Liang, Tian Shen [Faculty of Engineering and Technology, Multimedia University, 75450 Melaka (Malaysia); Hung, Yew Mun [School of Engineering, Monash University, 46150 Bandar Sunway (Malaysia)
2010-11-15
Experimental investigation is carried out to study the thermal performance of a heat sink with finned U-shape heat pipes which is a contemporary central processing unit (CPU) cooler compatible for a wide range of high-frequency microprocessors. The optimum range of operating heat load based on thermal resistance analysis of the heat sink is characterized. The convection heat transfer coefficient between the fins and the ambient air is estimated by using Bessel's modified equation in conjunction with the results obtained through the experimental investigation. The thermal optimization of the heat sink involves the determination of the optimized L-ratio (ratio of the evaporator section length to the condenser section length) of the U-shape heat pipe, by evaluating the minima of the thermal resistance function, in which case the empirical convection heat transfer coefficient is applied in the calculation. In conjunction with this, the optimal L-ratio of a U-shape heat pipe is found to be dependent on other geometrical parameters such as the heat pipe diameter and the fin spacing, which are of practical engineering importance in the optimum design of the heat sink. (author)
Introduction. Computational aerodynamics.
Tucker, Paul G
2007-10-15
The wide range of uses of computational fluid dynamics (CFD) for aircraft design is discussed along with its role in dealing with the environmental impact of flight. Enabling technologies, such as grid generation and turbulence models, are also considered along with flow/turbulence control. The large eddy simulation, Reynolds-averaged Navier-Stokes and hybrid turbulence modelling approaches are contrasted. The CFD prediction of numerous jet configurations occurring in aerospace are discussed along with aeroelasticity for aeroengine and external aerodynamics, design optimization, unsteady flow modelling and aeroengine internal and external flows. It is concluded that there is a lack of detailed measurements (for both canonical and complex geometry flows) to provide validation and even, in some cases, basic understanding of flow physics. Not surprisingly, turbulence modelling is still the weak link along with, as ever, a pressing need for improved (in terms of robustness, speed and accuracy) solver technology, grid generation and geometry handling. Hence, CFD, as a truly predictive and creative design tool, seems a long way off. Meanwhile, extreme practitioner expertise is still required and the triad of computation, measurement and analytic solution must be judiciously used.
A climatology of formation conditions for aerodynamic contrails
Directory of Open Access Journals (Sweden)
K. Gierens
2013-06-01
Full Text Available Aerodynamic contrails are defined in this paper as line shaped ice clouds caused by aerodynamically triggered cooling over the wings of an aircraft in cruise which become visible immediately at the trailing edge of the wing or close to it. Effects at low altitudes like condensation to liquid droplets and their potential heterogeneous freezing are excluded from our definition. We study atmospheric conditions that allow formation of aerodynamic contrails. These conditions are stated and then applied to atmospheric data, first to a special case where an aerodynamic contrail was actually observed and then to a full year of global reanalysis data. We show where, when (seasonal variation, and how frequently (probability aerodynamic contrails can form, and how this relates to actual patterns of air traffic. We study the formation of persistent aerodynamic contrails as well. Finally we check whether aerodynamic and exhaust contrails can coexist in the atmosphere. We show that visible aerodynamic contrails are possible only in an altitude range between roughly 540 and 250 hPa, and that the ambient temperature is the most important parameter, not the relative humidity. Finally we give an argument for our believe that currently aerodynamic contrails have a much smaller climate effect than exhaust contrails, which may however change in future with more air traffic in the tropics.
Institute of Scientific and Technical Information of China (English)
刘南; 白俊强; 邱亚松; 华俊
2015-01-01
在飞行器设计过程中为了提高优化设计的寻优精度，设计变量不断增加，从而使整个过程更加复杂且大幅延长设计周期。针对这一问题，基于本征正交分解降阶方法开展气动外形设计空间重构方面的研究。工作针对二维翼型开展，主要目标分为2个方面：①减少优化过程中的气动外形设计参数；②提高设计空间中满足设计约束的样本比例。在Hicks⁃Henne参数化和POD重构得到设计空间内随机选择20000个样本发现，Hicks⁃Henne参数化空间中满足设计约束的样本比例不足25％，而重构之后的空间则超过70％。因此，采用P OD方法对设计空间进行重构大大提高了样本质量，同时减少了优化设计参数。以RAE2822进行厚度约束下的单目标升阻比增大优化设计为例分别研究传统的约束处理方法和设计空间重构对优化结果的影响。传统约束处理方法中包括罚函数法和拒绝策略，优化结果表明拒绝策略略优于罚函数法，且无须设置惩罚权重，使用方便。对比重构前后设计空间的优化结果可见，2种传统约束处理方法在32个Hicks⁃Henne参数化空间中最优设计结果升阻比增加分别为27�61％和28�20％，采用P OD方法重构后的设计空间得到的升阻比提升分别为28�20％和30�63％。因此，设计空间重构前后的优化精度基本类似，而且设计空间重构之后优化设计参数大大减少，设计效率得到明显提升。%In order to increase optimization precision in the design process of aircraft, the design parameters have augmented;this makes the design process more complicated and extends the design cycle. Aiming at this issue, re⁃construction method of aerodynamic design space using Proper Orthogonal Decomposition is investigated. Main ob⁃jective is divided into two aspects: one is reduction of the number of aerodynamic design parameters in design
Holmes, Tim; Zanker, Johannes M
2013-01-01
Studying aesthetic preference is notoriously difficult because it targets individual experience. Eye movements provide a rich source of behavioral measures that directly reflect subjective choice. To determine individual preferences for simple composition rules we here use fixation duration as the fitness measure in a Gaze Driven Evolutionary Algorithm (GDEA), which has been demonstrated as a tool to identify aesthetic preferences (Holmes and Zanker, 2012). In the present study, the GDEA was used to investigate the preferred combination of color and shape which have been promoted in the Bauhaus arts school. We used the same three shapes (square, circle, triangle) used by Kandinsky (1923), with the three color palette from the original experiment (A), an extended seven color palette (B), and eight different shape orientation (C). Participants were instructed to look for their preferred circle, triangle or square in displays with eight stimuli of different shapes, colors and rotations, in an attempt to test for a strong preference for red squares, yellow triangles and blue circles in such an unbiased experimental design and with an extended set of possible combinations. We Tested six participants extensively on the different conditions and found consistent preferences for color-shape combinations for individuals, but little evidence at the group level for clear color/shape preference consistent with Kandinsky's claims, apart from some weak link between yellow and triangles. Our findings suggest substantial inter-individual differences in the presence of stable individual associations of color and shapes, but also that these associations are robust within a single individual. These individual differences go some way toward challenging the claims of the universal preference for color/shape combinations proposed by Kandinsky, but also indicate that a much larger sample size would be needed to confidently reject that hypothesis. Moreover, these experiments highlight the
Mendoza, Carlos S.; Safdar, Nabile; Myers, Emmarie; Kittisarapong, Tanakorn; Rogers, Gary F.; Linguraru, Marius George
2013-02-01
Craniosynostosis (premature fusion of skull sutures) is a severe condition present in one of every 2000 newborns. Metopic craniosynostosis, accounting for 20-27% of cases, is diagnosed qualitatively in terms of skull shape abnormality, a subjective call of the surgeon. In this paper we introduce a new quantitative diagnostic feature for metopic craniosynostosis derived optimally from shape analysis of CT scans of the skull. We built a robust shape analysis pipeline that is capable of obtaining local shape differences in comparison to normal anatomy. Spatial normalization using 7-degree-of-freedom registration of the base of the skull is followed by a novel bone labeling strategy based on graph-cuts according to labeling priors. The statistical shape model built from 94 normal subjects allows matching a patient's anatomy to its most similar normal subject. Subsequently, the computation of local malformations from a normal subject allows characterization of the points of maximum malformation on each of the frontal bones adjacent to the metopic suture, and on the suture itself. Our results show that the malformations at these locations vary significantly (p<0.001) between abnormal/normal subjects and that an accurate diagnosis can be achieved using linear regression from these automatic measurements with an area under the curve for the receiver operating characteristic of 0.97.
Directory of Open Access Journals (Sweden)
Sina Lohrasbi
2016-09-01
Full Text Available Latent Heat Thermal Energy Storage Systems (LHTESS containing Phase Change Material (PCM are used to establish balance between energy supply and demand. PCMs have high latent heat but low thermal conductivity, which affects their heat transfer performance. In this paper, a novel fin array has been optimized by multi-objective Response Surface Method (RSM based on discharging process of PCM, and then this fin configuration is applied on LHTESS, and comparison between full discharging time by applying this fin array and LHTESS with other fin structures has been carried out. The employed numerical method in this paper is Standard Galerkin Finite Element Method. Adaptive grid refinement is used to solve the equations. Since the enhancement technique, which has been employed in the present study reduces the employed PCM mass, maximum energy storage capacity variations have been considered. Therefore phase change expedition and maximum energy storage capacity have been considered as the objectives of optimization and the importance of second objective is indicated which is proposed as the novelty here. Results indicate that considering maximum energy storage capacity as the objective of optimization procedure leads to efficient shape design of LHTESS. Also employing optimized V-shaped fin in LHTESS, expedites discharging process considerably in comparison with the LHTESS without fin.
Shape slack: a design-manufacturing co-optimization methodology using tolerance information
Banerjee, Shayak; Agarwal, Kanak B.; Nassif, Sani; Orshansky, Michael
2013-01-01
The move to low-k1 lithography makes it increasingly difficult to print feature sizes that are a small fraction of the wavelength of light. With further delay in the delivery of extreme ultraviolet lithography, these difficulties will motivate the research community to explore increasingly broad solutions. We propose that there is significant research potential in studying the essential premise of the design/manufacturing handoff paradigm. Today this premise revolves around design rules that define what implementations are legal, and raw shapes, which define design intent, and are treated as a fixed requirement for lithography. In reality, layout features may vary within certain tolerances without violating any design constraints. The knowledge of such tolerances can help improve the manufacturability of layout features while still meeting design requirements. We propose a methodology to convert electrical slack in a design to shape slack or tolerances on individual layout shapes. We show how this can be done for two important implementation fabrics: (a) cell-library-based digital logic and (b) static random access memory. We further develop a tolerance-driven optical proximity correction algorithm that utilizes this shape slack information during mask preparation to ensure that all features prints within their shape slacks in presence of lithographic process variations. Experiments on 45 nm silicon on insulator cells using accurate process models show that this approach reduces postlithography delay errors by 50%, and layout hotspots by 47% compared to conventional methods.
Bat flight: aerodynamics, kinematics and flight morphology.
Hedenström, Anders; Johansson, L Christoffer
2015-03-01
Bats evolved the ability of powered flight more than 50 million years ago. The modern bat is an efficient flyer and recent research on bat flight has revealed many intriguing facts. By using particle image velocimetry to visualize wake vortices, both the magnitude and time-history of aerodynamic forces can be estimated. At most speeds the downstroke generates both lift and thrust, whereas the function of the upstroke changes with forward flight speed. At hovering and slow speed bats use a leading edge vortex to enhance the lift beyond that allowed by steady aerodynamics and an inverted wing during the upstroke to further aid weight support. The bat wing and its skeleton exhibit many features and control mechanisms that are presumed to improve flight performance. Whereas bats appear aerodynamically less efficient than birds when it comes to cruising flight, they have the edge over birds when it comes to manoeuvring. There is a direct relationship between kinematics and the aerodynamic performance, but there is still a lack of knowledge about how (and if) the bat controls the movements and shape (planform and camber) of the wing. Considering the relatively few bat species whose aerodynamic tracks have been characterized, there is scope for new discoveries and a need to study species representing more extreme positions in the bat morphospace.
Length optimization of an S-shaped transition between offset optical waveguides.
Marcuse, D
1978-03-01
We derive expressions for the radiation loss of an S-shaped waveguide transition used to connect two straight integrated optics waveguides that are offset with respect to each other. It is assumed that the diffused integrated optics waveguides are produced with the help of an electron beam machine that allows beam positioning in the y direction only in discrete steps. We thus must consider staircase approximations to the desired smooth S-shaped curves. A waveguide whose axis consists of a staircase suffers radiation losses due to the quasi-periodic deformation of its axis. A second loss contribution comes from the S-shape of the waveguide axis. The sum of these loss contributions assumes a minimum that defines the optimum length of the transition waveguide.
Directory of Open Access Journals (Sweden)
Tim eHolmes
2013-12-01
Full Text Available Studying aesthetic preference is notoriously difficult because it targets individual experience. Eye movements provide a rich source of behavioural measures that directly reflect subjective choice. To determine individual preferences for simple composition rules we here use fixation duration as the fitness measure in a Gaze Driven Evolutionary Algorithm (GDEA, which has been used as a tool to identify aesthetic preferences (Holmes & Zanker, 2012. In the present study, the GDEA was used to investigate the preferred combination of colour and shape which have been promoted in the Bauhaus arts school. We used the same 3 shapes (square, circle, triangle used by Kandinsky (1923, with the 3 colour palette from the original experiment (A, an extended 7 colour palette (B, and 8 different shape orientation (C. Participants were instructed to look for their preferred circle, triangle or square in displays with 8 stimuli of different shapes, colours and rotations, in an attempt to test for a strong preference for red squares, yellow triangles and blue circles in such an unbiased experimental design and with an extended set of possible combinations. We Tested 6 participants extensively on the different conditions and found consistent preferences for individuals, but little evidence at the group level for preference consistent with Kandinsky’s claims, apart from some weak link between yellow and triangles. Our findings suggest substantial inter-individual differences in the presence of stable individual associations of colour and shapes, but also that these associations are robust within a single individual. These individual differences go some way towards challenging the claims of the universal preference for colour/shape combinations proposed by Kandinsky, but also indicate that a much larger sample size would be needed to confidently reject that hypothesis. Moreover, these experiments highlight the vast potential of the GDEA in experimental aesthetics
Horstman, Raymond H.
1992-01-01
Aerodynamic flow achieved by adding fixed fairings to butterfly valve. When valve fully open, fairings align with butterfly and reduce wake. Butterfly free to turn, so valve can be closed, while fairings remain fixed. Design reduces turbulence in flow of air in internal suction system. Valve aids in development of improved porous-surface boundary-layer control system to reduce aerodynamic drag. Applications primarily aerospace. System adapted to boundary-layer control on high-speed land vehicles.
Topology and shape optimization of induced-charge electro-osmotic micropumps
DEFF Research Database (Denmark)
Gregersen, Misha Marie; Okkels, Fridolin; Bazant, M. Z.;
2009-01-01
For a dielectric solid surrounded by an electrolyte and positioned inside an externally biased parallel-plate capacitor, we study numerically how the resulting induced-charge electro-osmotic (ICEO) flow depends on the topology and shape of the dielectric solid. In particular, we extend existing...
Tong, Jiajun; Shelley, Michael
2016-11-01
It has been shown experimentally that swimming of nanoscale rod-like bi-metallic swimmers can be biased and guided by an array of teardrop shaped posts in the solution, giving rise to a statistically directed motion in long time. This could be useful in many applications like concentrating nanoswimmers, or separating them from non-motile particles. We pose a model to study such directed swimming, taking into account the absorption and desorption of the swimmers to the vertical walls of posts. We emphasize the role of varying curvature along the circumference of a single post on the absorption and desorption. In seeking to enhance directed swimming, we apply shape optimization to find how we can design, based on experimental data, better posts which have higher efficiency of transporting swimmers. This work was partially supported by the National Science Foundation under Award Number DMS-1463962.
Design of a shape adaptive airfoil actuated by a Shape Memory Alloy strip for airplane tail
Shirzadeh, R.; Raissi Charmacani, K.; Tabesh, M.
2011-04-01
Of the factors that mainly affect the efficiency of the wing during a special flow regime, the shape of its airfoil cross section is the most significant. Airfoils are generally designed for a specific flight condition and, therefore, are not fully optimized in all flight conditions. It is very desirable to have an airfoil with the ability to change its shape based on the current regime. Shape memory alloy (SMA) actuators activate in response to changes in the temperature and can recover their original configuration after being deformed. This study presents the development of a method to control the shape of an airfoil using SMA actuators. To predict the thermomechanical behaviors of an SMA thin strip, 3D incremental formulation of the SMA constitutive model is implemented in FEA software package ABAQUS. The interactions between the airfoil structure and SMA thin strip actuator are investigated. Also, the aerodynamic performance of a standard airfoil with a plain flap is compared with an adaptive airfoil.
A climatology of formation conditions for aerodynamic contrails
Directory of Open Access Journals (Sweden)
K. Gierens
2013-11-01
Full Text Available Aircraft at cruise levels can cause two kinds of contrails, the well known exhaust contrails and the less well-known aerodynamic contrails. While the possible climate impact of exhaust contrails has been studied for many years, research on aerodynamic contrails began only a few years ago and nothing is known about a possible contribution of these ice clouds to climate impact. In order to make progress in this respect, we first need a climatology of their formation conditions and this is given in the present paper. Aerodynamic contrails are defined here as line shaped ice clouds caused by aerodynamically triggered cooling over the wings of an aircraft in cruise which become visible immediately at the trailing edge of the wing or close to it. Effects at low altitudes like condensation to liquid droplets and their potential heterogeneous freezing are excluded from our definition. We study atmospheric conditions that allow formation of aerodynamic contrails. These conditions are stated and then applied to atmospheric data: first to a special case where an aerodynamic contrail was actually observed and then to a full year of global reanalysis data. We show where, when (seasonal variation, and how frequently (probability aerodynamic contrails can form, and how this relates to actual patterns of air traffic. We study the formation of persistent aerodynamic contrails as well. Furthermore, we check whether aerodynamic and exhaust contrails can coexist in the atmosphere. We show that visible aerodynamic contrails are possible only in an altitude range between roughly 540 and 250 hPa, and that the ambient temperature is the most important parameter, not the relative humidity. Finally, we argue that currently aerodynamic contrails have a much smaller climate effect than exhaust contrails, which may however change in future with more air traffic in the tropics.
So, Seulgi; Peschel, Ulf; Schmuki, Patrik
2016-01-01
In the present work, we introduce the anodic growth of conical shaped TiO2 nanotube arrays. These titania nanocones provide a scaffold for dye-sensitized solar cell (DSSC) structures with significantly improved photon management, providing an optimized absorption profile compared with conventional cylindrical nanotube arrays. Finite difference time domain (FDTD) modelling demonstrates a drastically changed power-absorption characteristic over the tube length. When used in a back-side illumination DSSC configuration, nanocone structures can reach over 60 % higher solar cell conversion efficiency than conventional tubes. The resulting {\\eta} of ca. 8 % represents one of the highest reported values for Graetzel type DSSCs used under back-side illumination.
Aerostructural Level Set Topology Optimization for a Common Research Model Wing
Dunning, Peter D.; Stanford, Bret K.; Kim, H. Alicia
2014-01-01
The purpose of this work is to use level set topology optimization to improve the design of a representative wing box structure for the NASA common research model. The objective is to minimize the total compliance of the structure under aerodynamic and body force loading, where the aerodynamic loading is coupled to the structural deformation. A taxi bump case was also considered, where only body force loads were applied. The trim condition that aerodynamic lift must balance the total weight of the aircraft is enforced by allowing the root angle of attack to change. The level set optimization method is implemented on an unstructured three-dimensional grid, so that the method can optimize a wing box with arbitrary geometry. Fast matching and upwind schemes are developed for an unstructured grid, which make the level set method robust and efficient. The adjoint method is used to obtain the coupled shape sensitivities required to perform aerostructural optimization of the wing box structure.
Optimized V-shape design of GaN nanodiodes for the generation of Gunn oscillations
Millithaler, J.-F.; Iñiguez-de-la-Torre, I.; Iñiguez-de-la-Torre, A.; González, T.; Sangaré, P.; Ducournau, G.; Gaquière, C.; Mateos, J.
2014-02-01
In this work, recent advances in the design of GaN planar Gunn diodes with asymmetric shape, so-called self-switching diodes, are presented. A particular geometry for the nanodiode is proposed, referred as V-shape, where the width of the channel is intentionally increased as approaching the anode. This design, which reduces the effect of the surface-charges at the anode side, is the most favourable one for the onset of Gunn oscillations, which emerge at lower current levels and with lower threshold voltages as compared to the standard square geometry, thus enhancing the power efficiency of the self-switching diode as sub-millimeter wave emitters.
Hashimoto, Hiroshi; Kim, Min-Geun; Abe, Kazuhisa; Cho, Seonho
2013-10-01
This paper presents a level set-based topology optimization method for noise barriers formed from an assembly of scatterers. The scattering obstacles are modeled by elastic bodies arranged periodically along the wall. Due to the periodicity, the problem can be reduced to that in a unit cell. The interaction between the elastic scatterers and the acoustic field is described in the context of the level set analysis. The semi-infinite acoustic wave regions located on the both sides of the barrier are represented by impedance matrices. The objective function is defined by the energy transmission passing the barrier. The design sensitivity is evaluated analytically by the aid of adjoint equations. The dependency of the optimal profile on the stiffness of scatterers and on the target frequency band is examined. The feasibility of the developed optimization method is proved through numerical examples.
Guerrero, R. D.; Arango, C. A.; Reyes, A.
2016-07-01
We recently proposed a Quantum Optimal Control (QOC) method constrained to build pulses from analytical pulse shapes [R. D. Guerrero et al., J. Chem. Phys. 143(12), 124108 (2015)]. This approach was applied to control the dissociation channel yields of the diatomic molecule KH, considering three potential energy curves and one degree of freedom. In this work, we utilized this methodology to study the strong field control of the cis-trans photoisomerization of 11-cis retinal. This more complex system was modeled with a Hamiltonian comprising two potential energy surfaces and two degrees of freedom. The resulting optimal pulse, made of 6 linearly chirped pulses, was capable of controlling the population of the trans isomer on the ground electronic surface for nearly 200 fs. The simplicity of the pulse generated with our QOC approach offers two clear advantages: a direct analysis of the sequence of events occurring during the driven dynamics, and its reproducibility in the laboratory with current laser technologies.
Muthalif, Asan G. A.; Nordin, N. H. Diyana
2015-03-01
Harvesting energy from the surroundings has become a new trend in saving our environment. Among the established ones are solar panels, wind turbines and hydroelectric generators which have successfully grown in meeting the world's energy demand. However, for low powered electronic devices; especially when being placed in a remote area, micro scale energy harvesting is preferable. One of the popular methods is via vibration energy scavenging which converts mechanical energy (from vibration) to electrical energy by the effect of coupling between mechanical variables and electric or magnetic fields. As the voltage generated greatly depends on the geometry and size of the piezoelectric material, there is a need to define an optimum shape and configuration of the piezoelectric energy scavenger. In this research, mathematical derivations for unimorph piezoelectric energy harvester are presented. Simulation is done using MATLAB and COMSOL Multiphysics software to study the effect of varying the length and shape of the beam to the generated voltage. Experimental results comparing triangular and rectangular shaped piezoelectric beam are also presented.
Aerodynamic optimisation of an industrial axial fan blade
2006-01-01
Numerical optimisation methods have successfully been used for a variety of aerodynamic design problems over quite a few years. However the application of these methods to the aerodynamic blade shape optimisation of industrial axial fans has received much less attention in the literature probably given the fact that the majority of resources available to develop these automated design approaches is to be found in the aerospace field. This work presents the develo...
Hydrodynamic analysis and shape optimization for vertical axisymmetric wave energy converters
Zhang, Wan-chao; Liu, Heng-xu; Zhang, Liang; Zhang, Xue-wei
2016-12-01
The absorber is known to be vertical axisymmetric for a single-point wave energy converter (WEC). The shape of the wetted surface usually has a great influence on the absorber's hydrodynamic characteristics which are closely linked with the wave power conversion ability. For complex wetted surface, the hydrodynamic coefficients have been predicted traditionally by hydrodynamic software based on the BEM. However, for a systematic study of various parameters and geometries, they are too multifarious to generate so many models and data grids. This paper examines a semi-analytical method of decomposing the complex axisymmetric boundary into several ring-shaped and stepped surfaces based on the boundary discretization method (BDM) which overcomes the previous difficulties. In such case, by using the linear wave theory based on eigenfunction expansion matching method, the expressions of velocity potential in each domain, the added mass, radiation damping and wave excitation forces of the oscillating absorbers are obtained. The good astringency of the hydrodynamic coefficients and wave forces are obtained for various geometries when the discrete number reaches a certain value. The captured wave power for a same given draught and displacement for various geometries are calculated and compared. Numerical results show that the geometrical shape has great effect on the wave conversion performance of the absorber. For absorbers with the same outer radius and draught or displacement, the cylindrical type shows fantastic wave energy conversion ability at some given frequencies, while in the random sea wave, the parabolic and conical ones have better stabilization and applicability in wave power conversion.
Optimal shape of a cold-neutron triple-axis spectrometer
Energy Technology Data Exchange (ETDEWEB)
Lefmann, K., E-mail: lefmann@fys.ku.d [Nanoscience and eScience Centers, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen O (Denmark); European Spallation Source, University of Lund, St. Algatan 4, Lund (Sweden); Filges, U. [Laboratory for Development and Methods, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Treue, F. [Nanoscience and eScience Centers, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen O (Denmark); Kirkensgard, J.J.K. [Institute of Nature and Models, Roskilde University (Denmark); Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen (Denmark); Plesner, B. [Institute of Nature and Models, Roskilde University (Denmark); Hansen, K.S. [Institute of Nature and Models, Roskilde University (Denmark); Mid-Greenland High School, Nuuk, Greenland (Denmark); Kleno, K.H. [Nanoscience and eScience Centers, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen O (Denmark); European Spallation Source, University of Lund, St. Algatan 4, Lund (Sweden)
2011-04-01
We have performed a McStas optimization of the primary spectrometer for a generic 40 m long, cold-neutron triple-axis spectrometer with a doubly focusing monochromator. The optimal design contains an elliptically focusing guide, a virtual source point before a low-grade PG monochromator, and non-equidistant focusing at the monochromator. The flux at 5 meV shows a gain factor 12 over the 'classical' design with a straight 12x3cm{sup 2}, m=2 guide and a vertically focusing PG monochromator. In addition, the energy resolution was found to be improved. This unexpectedly large design improvement agrees with the Liouville theorem and can be understood as the product of many smaller gain factors, combined with a more optimal utilization of the beam divergence within the guide. Our results may be relevant for a possible upgrade of a number of cold-neutron triple-axis spectrometers-and for a possible triple-axis spectrometer at the European Spallation Source.
Optimal shape of a cold-neutron triple-axis spectrometer
Lefmann, K.; Filges, U.; Treue, F.; Kirkensgård, J. J. K.; Plesner, B.; Hansen, K. S.; Klenø, K. H.
2011-04-01
We have performed a McStas optimization of the primary spectrometer for a generic 40 m long, cold-neutron triple-axis spectrometer with a doubly focusing monochromator. The optimal design contains an elliptically focusing guide, a virtual source point before a low-grade PG monochromator, and non-equidistant focusing at the monochromator. The flux at 5 meV shows a gain factor 12 over the “classical” design with a straight 12×3cm2, m=2 guide and a vertically focusing PG monochromator. In addition, the energy resolution was found to be improved. This unexpectedly large design improvement agrees with the Liouville theorem and can be understood as the product of many smaller gain factors, combined with a more optimal utilization of the beam divergence within the guide. Our results may be relevant for a possible upgrade of a number of cold-neutron triple-axis spectrometers—and for a possible triple-axis spectrometer at the European Spallation Source.
On cup anemometer rotor aerodynamics.
Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio
2012-01-01
The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.
On Cup Anemometer Rotor Aerodynamics
Directory of Open Access Journals (Sweden)
Santiago Pindado
2012-05-01
Full Text Available The influence of anemometer rotor shape parameters, such as the cups’ front area or their center rotation radius on the anemometer’s performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal, tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups’ center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor’s cup.
DEFF Research Database (Denmark)
Shu, Chuan-Cun; Henriksen, Niels E.
2012-01-01
We implement phase-only shaped laser pulses within quantum optimal control theory for laser-molecule interaction. This approach is applied to the indirect photofragmentation dynamics of NaI in the weak-field limit. It is shown that optimized phase-modulated pulses with a fixed frequency...
Directory of Open Access Journals (Sweden)
Šćepanović Miodrag
2013-01-01
Full Text Available Bacground/Aim. Retentive force of removable partial denture (RPD directly depends on elastic force of stretched retentive clasp arms (RCAs. During deflection RCA must have even stress distribution. Safety factor is the concept which can be applied in estimating durability and functionality of RCAs. This study was based on analyzing properties of clasps designed by conventional clasp wax profiles and defining the optimal shapes of RCAs for stress distribution and safety factor aspects. Methods. Computer-aided-design (CAD models of RCAs with simulated properties of materials used for fabrication of RPD cobalt-chromium-molybdenum (CoCrMo alloy, commercially pure titanium (CPTi and polyacetale were analyzed. Results. The research showed that geometrics of Rapidflex profiles from the BIOS concept are defined for designing and modeling RCAs from CoCrMo alloys. I-Bar and Bonihard clasps made from CPTi might have the same design as Co- CrMo clasp only by safety factor aspect, but it is obvious that CPTi are much more flexible, so their shape must be more massive. Polyacetale clasps should not be fabricated by BIOS concept for CoCrMo alloy. A proof for that is the low value of safety factor. Conclusion. The BIOS concept should be used only for RCAs made of CoCrMo alloy and different wax profiles should be used for fabricating clasps of other investigated materials. The contribution of this study may be the improvement of present systems for defining the clasps shapes made from CoCrMo alloys. The more significant application is possibility of creating new concepts in defining shapes of RCA made from CPTi and polyacetale.
Pseudo-time method for optimal shape design using the Euler equations
Iollo, Angelo; Kuruvila, Geojoe; Ta'asan, Shlomo
1995-01-01
We exploit a novel idea for the optimization of flows governed by the Euler equations. The algorithm consists of marching on the design hypersurface while improving the distance to the state and costate hypersurfaces. We consider the problem of matching the pressure distribution to a desired one, subject to the euler equations, both for subsonic and supersonic flows. The rate of convergence to the minimum for the cases considered is 3 to 4 times slower than that of the analysis problem. Results are given for Ringleb flow and a shockless recompression case.
Arbitrary Shape Deformation in CFD Design
Landon, Mark; Perry, Ernest
2014-01-01
Sculptor(R) is a commercially available software tool, based on an Arbitrary Shape Design (ASD), which allows the user to perform shape optimization for computational fluid dynamics (CFD) design. The developed software tool provides important advances in the state-of-the-art of automatic CFD shape deformations and optimization software. CFD is an analysis tool that is used by engineering designers to help gain a greater understanding of the fluid flow phenomena involved in the components being designed. The next step in the engineering design process is to then modify, the design to improve the components' performance. This step has traditionally been performed manually via trial and error. Two major problems that have, in the past, hindered the development of an automated CFD shape optimization are (1) inadequate shape parameterization algorithms, and (2) inadequate algorithms for CFD grid modification. The ASD that has been developed as part of the Sculptor(R) software tool is a major advancement in solving these two issues. First, the ASD allows the CFD designer to freely create his own shape parameters, thereby eliminating the restriction of only being able to use the CAD model parameters. Then, the software performs a smooth volumetric deformation, which eliminates the extremely costly process of having to remesh the grid for every shape change (which is how this process had previously been achieved). Sculptor(R) can be used to optimize shapes for aerodynamic and structural design of spacecraft, aircraft, watercraft, ducts, and other objects that affect and are affected by flows of fluids and heat. Sculptor(R) makes it possible to perform, in real time, a design change that would manually take hours or days if remeshing were needed.
Verma, Aekaansh; Shang, Jessica; Esmaily-Moghadam, Mahdi; Wong, Kwai; Marsden, Alison
2016-11-01
Babies born with a single functional ventricle typically undergo three open-heart surgeries starting as neonates. The first of these stages (BT shunt or Norwood) has the highest mortality rates of the three, approaching 30%. Proceeding directly to a stage-2 Glenn surgery has historically demonstrated inadequate pulmonary flow (PF) & high mortality. Recently, the Assisted Bi-directional Glenn (ABG) was proposed as a promising means to achieve a stable physiology by assisting the PF via an 'ejector pump' from the systemic circulation. We present preliminary parametrization and optimization results for the ABG geometry, with the goal of increasing PF. To limit excessive pressure increases in the Superior Vena Cava (SVC), the SVC pressure is included as a constraint. We use 3-D finite element flow simulations coupled with a single ventricle lumped parameter network to evaluate PF & the pressure constraint. We employ a derivative free optimization method- the Surrogate Management Framework, in conjunction with the OpenDIEL framework to simulate multiple simultaneous evaluations. Results show that nozzle diameter is the most important design parameter affecting ABG performance. The application of these results to patient specific situations will be discussed. This work was supported by an NSF CAREER award (OCI1150184) and by the XSEDE National Computing Resource.
Shape optimization of rotating rectangular channels with pin-fins by kriging method
Energy Technology Data Exchange (ETDEWEB)
Moon, Mi Ae; Husain, Afzal; Kim, Kwang Yong [Inha Univ., Incheon (Korea, Republic of)
2009-07-01
This paper presents numerical optimization of the design of a rotating rectangular channel with staggered arrays of pin-fins with Kriging metamodeling technique. Two non-dimensional variables, the ratio of the height to diameter of the pin-fin and the ratio of the spacing between the pin-fins to diameter of the pin-fins are chosen as design variables. The objective function as a linear combination of heat transfer and friction loss related terms with a weighting factor is selected for the optimization. Objective function values at twenty training points generated by Latin Hypercube Sampling (LHS) are evaluated by three-dimensional ReynoldsAveraged Navier-Stokes (RANS) method with the Shear Stress Transport (SST) turbulence model. The prediction of objective function by Kriging metamodeling at optimum point shows reasonable accuracy in comparison with the values calculated by RANS analysis. With increase in height of the pin-fin, heat transfer is decreased and at the same time pressure drop is also decreased, while opposite behavior is obtained for the pin-fin spacing.
Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence
DEFF Research Database (Denmark)
Sørensen, Jens Nørkær
2014-01-01
In order to design and operate a wind farm optimally it is necessary to know in detail how the wind behaves and interacts with the turbines in a farm. This not only requires knowledge about meteorology, turbulence and aerodynamics, but it also requires access to powerful computers and efficient...... software. Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence was established in 2010 in order to create a world-leading cross-disciplinary flow center that covers all relevant disciplines within wind farm meteorology and aerodynamics....
Hysteresis Curve Fitting Optimization of Magnetic Controlled Shape Memory Alloy Actuator
Directory of Open Access Journals (Sweden)
Fuquan Tu
2016-11-01
Full Text Available As a new actuating material, magnetic controlled shape memory alloys (MSMAs have excellent characteristics such as a large output strain, fast response, and high energy density. These excellent characteristics are very attractive for precision positioning systems. However, the availability of MSMAs in practical precision positioning is poor, caused by weak repeatability under a certain stimulus. This problem results from the error of a large magnetic hysteresis in an external magnetic field. A suitable hysteresis modelling method can reduce the error and improve the accuracy of the MSMA actuator. After analyzing the original hysteresis modelling methods, three kinds of hysteresis modelling methods are proposed: least squares method, back propagation (BP artificial neural network, and BP artificial neural network based on genetic algorithms. Comparing the accuracy and convergence rate of three kinds of hysteresis modelling methods, the results show that the convergence rate of least squares method is the fastest, and the convergence accuracy of BP artificial neural networks based on genetic algorithms is the highest.
DEFF Research Database (Denmark)
Kleissl, Kenneth
to a categorization of the different control technics together with an identification of two key mechanisms for reduction of the design drag force. During this project extensive experimental work examining the aerodynamics of the currently used cable surface modifications together with new innovative proposals have...
Trajectory Optimization Design for Morphing Wing Missile
Institute of Scientific and Technical Information of China (English)
Ruisheng Sun; Chao Ming; Chuanjie Sun
2015-01-01
This paper presents a new particle swarm optimization ( PSO) algorithm to optimize the trajectory of morphing⁃wing missile so as to achieve the enlargement of the maximum range. Equations of motion for the two⁃dimensional dynamics are derived by treating the missile as an ideal controllable mass point. An investigation of aerodynamic characteristics of morphing⁃wing missile with varying geometries is performed. After deducing the optimizing trajectory model for maximizing range, a type of discrete method is put forward for taking optimization control problem into nonlinear dynamic programming problem. The optimal trajectory is solved by using PSO algorithm and penalty function method. The simulation results suggest that morphing⁃wing missile has the larger range than the fixed⁃shape missile when launched at supersonic speed, while morphing⁃wing missile has no obvious range increment than the fixed⁃shape missile at subsonic speed.
DEFF Research Database (Denmark)
Markus, D.; Ferri, Francesco; Wüchner, R.
2015-01-01
that focuses on differences in load curves resulting from 2D and 3D flows. It is shown that the major trends predicted by the numerical simulations are also captured in the experiment, highlighting the potential of CFD as a powerful tool for shape optimization studies. The overall aim of the paper...... variations of the structure on the resulting horizontal forces. Steady current conditions, dynamic loading due to waves, and combined wave–current scenarios are considered. A clear focus is put on simplicity and reproducibility, allowing for efficient testing of related methods and codes. This is achieved...... by defining a simple test geometry, altered in one design variable only, and by designing the test case such that a two dimensional analysis of the flow fields is possible. The force sensitivities to changes in the geometry are determined both numerically and experimentally for a great bandwidth of different...
Mahmoudzadeh Akherat, S. M. Javid; Cassel, Kevin; Hammes, Mary; Boghosian, Michael; Illinois Institute of Technology Team; University of Chicago Team
2016-11-01
Venous stenosis developed after the growth of excessive neointimal hyperplasia (NH) in chronic dialysis treatment is a major cause of mortality in renal failure patients. It has been hypothesized that the low wall shear stress (WSS) triggers an adaptive response in patients' venous system that through the growth of neointimal hyperplastic lesions restores WSS and transmural pressure, which also regulates the blood flow rate back to physiologically acceptable values which is violated by dialysis treatment. A strong coupling of three-dimensional CFD and shape optimization analyses were exploited to elucidate and forecast this adaptive response which correlates very well topographically with patient-specific clinical data. Based on the framework developed, a medical protocol is suggested to predict and prevent dialysis treatment failure in clinical practice. Supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health (R01 DK90769).
Unsteady Aerodynamic Flow Control of Moving Platforms
2014-05-29
This error will arguably be diminished further with the future tuning of the PID controller that implements the motor commands. III.3.3 Aerodynamic...model is still aligned with the flow or ‘fine tune ’ the SMA power if it needs a minor realignment. III.1.2 Centered Static Model Prior to examining...8217 fluidic control. In addition, a PID controller is developed to effect ’closed loop’ fluidic control with optimally timed synthetic jet operation
The optimal shape of elastomer mushroom-like fibers for high and robust adhesion
Directory of Open Access Journals (Sweden)
Burak Aksak
2014-05-01
Full Text Available Over the last decade, significant effort has been put into mimicking the ability of the gecko lizard to strongly and reversibly cling to surfaces, by using synthetic structures. Among these structures, mushroom-like elastomer fiber arrays have demonstrated promising performance on smooth surfaces matching the adhesive strengths obtained with the natural gecko foot-pads. It is possible to improve the already impressive adhesive performance of mushroom-like fibers provided that the underlying adhesion mechanism is understood. Here, the adhesion mechanism of bio-inspired mushroom-like fibers is investigated by implementing the Dugdale–Barenblatt cohesive zone model into finite elements simulations. It is found that the magnitude of pull-off stress depends on the edge angle θ and the ratio of the tip radius to the stalk radius β of the mushroom-like fiber. Pull-off stress is also found to depend on a dimensionless parameter χ, the ratio of the fiber radius to a length-scale related to the dominance of adhesive stress. As an estimate, the optimal parameters are found to be β = 1.1 and θ = 45°. Further, the location of crack initiation is found to depend on χ for given β and θ. An analytical model for pull-off stress, which depends on the location of crack initiation as well as on θ and β, is proposed and found to agree with the simulation results. Results obtained in this work provide a geometrical guideline for designing robust bio-inspired dry fibrillar adhesives.
水下机器人外形优化设计%Shape Optimal Design of Underwater Robot
Institute of Scientific and Technical Information of China (English)
王妹婷; 齐永锋; 汤方平; 戴志光; 陆柳延; 吕学智
2014-01-01
针对水下机器人水下航行时节约能源、减小阻力、提高航速的要求，采用数学线型设计方法，研究了水下机器人回转体外形优化。在排水量相同的条件下，应用流体计算软件Fluent计算并比较了几种不同回转体线型构造的水下机器人直航阻力，根据阻力最小原则并考虑内部元器件布置的空间需求，选择Myring线型方程构建水下机器人外形。根据两个型值点并应用软件Visual C＋＋，确定了Myring线型方程中首部锐度因子和尾部离去角两个参数，进而完成了符合机器人自身情况的外形优化设计。研究结果可达到降低水下机器人流线型回转体阻力、改善水动力性能的目的。%In the process of the underwater robot sailing,aiming at the requests for energy savings,reducing resistance and im-proving the speed,mathematical linetypes based design method was adopted to investigate shape optimal design of underwater robot. Under the conditions of the same displacement,adopting fluid calculation software Fluent,compare of linear sailing resistance of un-derwater robots structured separately by four different linetypes was executed. According to the principle of least resistance,considering the space requirements of the internal components layout,Myring linear equations were selected to build shape of underwater robot. Ac-cording to the two data points,adopting software Visual C+ +,the head sharpness factor and tail departure angle in Myring linetype equation were determined. After the two exterior parameters determined,shape optimal design of underwater robot was completed. The research results can reach to purposes for reducing the sailing resistance and improving the hydrodynamic performance of underwater ro-bot.
Directory of Open Access Journals (Sweden)
D. C. Tsamatsoulis
2014-03-01
Full Text Available Based on a dynamical model of the grinding process in closed circuit mills, efficient efforts have been made to optimize PID controllers of cement milling. The process simulation is combined with an autoregressive model of the errors between the actual process values and the computed ones. Long term industrial data have been used to determine the model parameters. The data include grinding of various cement types. The M - Constrained Integral Gain Optimization (MIGO loop shaping method is utilized to determine PID sets satisfying a certain robustness constraint. The maximum sensitivity is considered as such a criterion. Both dynamical parameters and PID sets constitute the inputs of a detailed simulator which involves all the main process characteristics. The simulation is applied over all the PID sets aiming to find the parameter region that provides the minimum integral of absolute error, which functions as a performance criterion. For each cement type a PID set is selected and put in operation in a closed circuit cement mill. The performance of the regulation is evaluated after a sufficient time period, concluding that the developed design combining criteria of both robustness and performance leads to PID controllers of high efficiency.
Institute of Scientific and Technical Information of China (English)
杨魏; 王宏; 吴玉林
2012-01-01
基于三维反问题设计方法和CFD技术,结合试验设计方法和模拟退火优化算法,以轴面流道形状参数和叶片形状参数为设计变量,以叶轮效率为优化目标,建立了离心风机叶轮三维反问题气动优化设计方法.叶片形状通过三维反问题设计方法由叶轮的环量分布参数表达.运用该方法进行了离心风机叶轮的优化设计,叶轮效率提高了3.3％.根据建立的优化设计变量和叶轮效率之间的响应面函数关系式,分析了不同轴面流道形状参数和环量分布参数及参数间交互效应对叶轮效率的影响.结果表明:相对于轮盘处轴面流道轮盖处型线和环量分布形式,轴面流道叶片进口边倾斜角对叶轮效率影响更为显著.%An optimization design method based on three-dimensional inverse design method and CFD was developed by combining design of experimental method, response surface method and simulated annealing optimization calculation. The shape parameters of meridional channel and blade were taken as optimization design parameters, and the impeller efficiency was setting as the optimization object. The shape parameters of the blade were expressed by velocity circulation distribution parameters through three-dimensional inverse design method. The optimization method was applied to a centrifugal fan impeller with the efficiency improved by 3.3%. The effects of the meridional channel shape parameters, circulation parameters and their interaction effects on the impeller efficiency were analyzed according to the constructed response surface between the design parameters and the impeller efficiency. It is shown that the lean angle of the blade leading edge on meridional channel played ah important role on the impeller efficiency. Compared with the hub, the shape curve and the circulation distribution shape on the shroud have more influences on the efficiency.
MULTIOBJECT OPTIMIZATION OF A CENTRIFUGAL IMPELLER USING EVOLUTIONARY ALGORITHMS
Institute of Scientific and Technical Information of China (English)
Li Jun; Liu Lijun; Feng Zhenping
2004-01-01
Application of the multiobjective evolutionary algorithms to the aerodynamic optimization design of a centrifugal impeller is presented. The aerodynamic performance of a centrifugal impeller is evaluated by using the three-dimensional Navier-Stokes solutions. The typical centrifugal impeller is redesigned for maximization of the pressure rise and blade load and minimization of the rotational total pressure loss at the given flow conditions. The B閦ier curves are used to parameterize the three-dimensional impeller blade shape. The present method obtains many reasonable Pareto optimal designs that outperform the original centrifugal impeller. Detailed observation of the certain Pareto optimal design demonstrates the feasibility of the present multiobjective optimization method tool for turbomachinery design.
Directory of Open Access Journals (Sweden)
Hanbing Liu
2016-11-01
Full Text Available Irregularly-shaped bridges are usually adopted to connect the main bridge and ramps in urban overpasses, which are under significant flexion-torsion coupling effects and in complicated stress states. In irregular-shaped bridge design, the parameters such as ramp radius, bifurcation diaphragm stiffness, box girder height, and supporting condition could affect structural performance in different manners. In this paper, the influence of various parameters on three indices, including maximum stress, the stress variation coefficient, and the fundamental frequency of torsional vibration, is investigated and analyzed based on orthogonal test method. Through orthogonal analysis, the major influence parameters and corresponding optimal values for these indices are achieved. Combining with the analytic hierarchy process (AHP, the hierarchical structure model of the multi-indices orthogonal test is established and a comprehensive weight analysis method is proposed to reflect the parameter influence on overall mechanical properties of an irregularly-shaped bridge. Influence order and optimal values of parameters for overall mechanical properties are determined based on the weight of factors and levels calculated by the comprehensive weight analysis method. The results indicate that the comprehensive weight analysis method is superior to the overall balance method, which verifies the effectiveness and accuracy of the comprehensive weight analysis in the parameter optimization of the multi-indices orthogonal test for an irregularly-shaped bridge. Optimal parameters obtained in this paper can provide reference and guidance for parameter control in irregularly-shaped bridge design.
Adaptive Aft Signature Shaping of a Low-Boom Supersonic Aircraft Using Off-Body Pressures
Ordaz, Irian; Li, Wu
2012-01-01
The design and optimization of a low-boom supersonic aircraft using the state-of-the- art o -body aerodynamics and sonic boom analysis has long been a challenging problem. The focus of this paper is to demonstrate an e ective geometry parameterization scheme and a numerical optimization approach for the aft shaping of a low-boom supersonic aircraft using o -body pressure calculations. A gradient-based numerical optimization algorithm that models the objective and constraints as response surface equations is used to drive the aft ground signature toward a ramp shape. The design objective is the minimization of the variation between the ground signature and the target signature subject to several geometric and signature constraints. The target signature is computed by using a least-squares regression of the aft portion of the ground signature. The parameterization and the deformation of the geometry is performed with a NASA in- house shaping tool. The optimization algorithm uses the shaping tool to drive the geometric deformation of a horizontal tail with a parameterization scheme that consists of seven camber design variables and an additional design variable that describes the spanwise location of the midspan section. The demonstration cases show that numerical optimization using the state-of-the-art o -body aerodynamic calculations is not only feasible and repeatable but also allows the exploration of complex design spaces for which a knowledge-based design method becomes less effective.
Aerodynamic Leidenfrost effect
Gauthier, Anaïs; Bird, James C.; Clanet, Christophe; Quéré, David
2016-12-01
When deposited on a plate moving quickly enough, any liquid can levitate as it does when it is volatile on a very hot solid (Leidenfrost effect). In the aerodynamic Leidenfrost situation, air gets inserted between the liquid and the moving solid, a situation that we analyze. We observe two types of entrainment. (i) The thickness of the air gap is found to increase with the plate speed, which is interpreted in the Landau-Levich-Derjaguin frame: Air is dynamically dragged along the surface and its thickness results from a balance between capillary and viscous effects. (ii) Air set in motion by the plate exerts a force on the levitating liquid. We discuss the magnitude of this aerodynamic force and show that it can be exploited to control the liquid and even to drive it against gravity.
Computational electromagnetic-aerodynamics
Shang, Joseph J S
2016-01-01
Presents numerical algorithms, procedures, and techniques required to solve engineering problems relating to the interactions between electromagnetic fields, fluid flow, and interdisciplinary technology for aerodynamics, electromagnetics, chemical-physics kinetics, and plasmadynamics This book addresses modeling and simulation science and technology for studying ionized gas phenomena in engineering applications. Computational Electromagnetic-Aerodynamics is organized into ten chapters. Chapter one to three introduce the fundamental concepts of plasmadynamics, chemical-physics of ionization, classical magnetohydrodynamics, and their extensions to plasma-based flow control actuators, high-speed flows of interplanetary re-entry, and ion thrusters in space exploration. Chapter four to six explain numerical algorithms and procedures for solving Maxwell’s equation in the time domain for computational electromagnetics, plasma wave propagation, and the time-dependent c mpressible Navier-Stokes equation for aerodyn...
Hypervelocity Aerodynamics and Control
1990-06-06
Report: Hypervelocity Aerodynamics and Control 12. PERSONAL AUTHOR(S) T. C. Adamson, Jr. and R. IA. Howe 13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE...6] pulse applied. If the Mxyz system as shown is Fig. 3 r 3. , is used, then we have R21= k costo -t4 ksin yot 1 6r= ro 1 (4) -- (6k 2 - 5 -30k 2 sin
Galvan-Sosa, M.; Portilla, J.; Hernandez-Rueda, J.; Siegel, J.; Moreno, L.; Solis, J.
2014-09-01
In this work, we have developed and implemented a powerful search strategy for optimization of nonlinear optical effects by means of femtosecond pulse shaping, based on topological concepts derived from quantum control theory. Our algorithm [Multiple One-Dimensional Search (MODS)] is based on deterministic optimization of a single solution rather than pseudo-random optimization of entire populations as done by commonly used evolutionary algorithms. We have tested MODS against a genetic algorithm in a nontrivial problem consisting in optimizing the Kerr gating signal (self-interaction) of a shaped laser pulse in a detuned Michelson interferometer configuration. The obtained results show that our search method (MODS) strongly outperforms the genetic algorithm in terms of both convergence speed and quality of the solution. These findings demonstrate the applicability of concepts of quantum control theory to nonlinear laser-matter interaction problems, even in the presence of significant experimental noise.
Shu, Chuan-Cun; Henriksen, Niels E
2012-01-28
We implement phase-only shaped laser pulses within quantum optimal control theory for laser-molecule interaction. This approach is applied to the indirect photofragmentation dynamics of NaI in the weak-field limit. It is shown that optimized phase-modulated pulses with a fixed frequency distribution can substantially modify transient dissociation probabilities as well as the momentum distribution associated with the relative motion of Na and I.
Effects of ice accretion on the aerodynamics of bridge cables
DEFF Research Database (Denmark)
Demartino, C.; Koss, Holger; Georgakis, Christos T.;
2015-01-01
Undesirable wind induced vibrations of bridge cables can occur when atmospheric conditions are such to generate ice accretion. This paper contains the results of an extensive investigation of the effects of ice accretion due to in-cloud icing, on the aerodynamic characteristics of bridge hangers...... and stay cables. The aim of this paper is twofold; first, it was investigated the ice accretion process and the final shape of the ice accreted; then the aerodynamics of the ice accreted bridge cables was characterized, and related to the ice shape. Different climatic conditions, i.e. combinations...... of the ice accretions is given in the paper. Only for the bridge hanger case, a short description of the evolution of the ice accretions is given. The aerodynamic force coefficients were then measured with varying yaw angle, angle of attack and wind speed, and are presented and discussed in the paper...
Noise aspects at aerodynamic blade optimisation projects
Energy Technology Data Exchange (ETDEWEB)
Schepers, J.G. [Netherlands Energy Research Foundation, Petten (Netherlands)
1997-12-31
This paper shows an example of an aerodynamic blade optimisation, using the program PVOPT. PVOPT calculates the optimal wind turbine blade geometry such that the maximum energy yield is obtained. Using the aerodynamic optimal blade design as a basis, the possibilities of noise reduction are investigated. The aerodynamic optimised geometry from PVOPT is the `real` optimum (up to the latest decimal). The most important conclusion from this study is, that it is worthwhile to investigate the behaviour of the objective function (in the present case the energy yield) around the optimum: If the optimum is flat, there is a possibility to apply modifications to the optimum configuration with only a limited loss in energy yield. It is obvious that the modified configurations emits a different (and possibly lower) noise level. In the BLADOPT program (the successor of PVOPT) it will be possible to quantify the noise level and hence to assess the reduced noise emission more thoroughly. At present the most promising approaches for noise reduction are believed to be a reduction of the rotor speed (if at all possible), and a reduction of the tip angle by means of low lift profiles, or decreased twist at the outboard stations. These modifications were possible without a significant loss in energy yield. (LN)
Aerodynamic data of space vehicles
Weiland, Claus
2014-01-01
The capacity and quality of the atmospheric flight performance of space flight vehicles is characterized by their aerodynamic data bases. A complete aerodynamic data base would encompass the coefficients of the static longitudinal and lateral motions and the related dynamic coefficients. In this book the aerodynamics of 27 vehicles are considered. Only a few of them did really fly. Therefore the aerodynamic data bases are often not complete, in particular when the projects or programs were more or less abruptly stopped, often due to political decisions. Configurational design studies or the development of demonstrators usually happen with reduced or incomplete aerodynamic data sets. Therefore some data sets base just on the application of one of the following tools: semi-empirical design methods, wind tunnel tests, numerical simulations. In so far a high percentage of the data presented is incomplete and would have to be verified. Flight mechanics needs the aerodynamic coefficients as function of a lot of var...
Vortical sources of aerodynamic force and moment
Wu, J. Z.; Wu, J. M.
1989-01-01
It is shown that the aerodynamic force and moment can be expressed in terms of vorticity distribution (and entropy variation for compressible flow) on near wake plane, or in terms of boundary vorticity flux on the body surface. Thus the vortical sources of lift and drag are clearly identified, which is the real physical basis of optimal aerodynamic design. Moreover, these sources are highly compact, hence allowing one to concentrate on key local regions of the configuration, which have dominating effect to the lift and drag. A detail knowledge of the vortical low requires measuring or calculating the vorticity and dilatation field, which is however still a challenging task. Nevertheless, this type of formulation has some unique advantages; and how to set up a well-posed problem, in particular how to establish vorticity-dilatation boundary conditions, is addressed.
Institute of Scientific and Technical Information of China (English)
王超; 高正红; 黄江涛; 赵轲; 李静; 许放
2015-01-01
The number of design variables and their design room are focused on in airfoil pa-rameterization.Fewer variables helps improve the speed of convergence and adequate design room can help to find the best result.However,they contradict with each other.A research was carried on the performances of basic Bezier-Spline curves and a comparison was presented between different orders of Bezier-Spline curves in order to explain their ability of describing a supercritical airfoil and aerodynamic errors as a result of geometric errors.An adding-order airfoil parameter-ization method was put forward based on the characteristics of Bezier-Spline curves.An optimiza-tion design system of expanding design room was established combined with improved particle swarm optimization algorithm which guarantees design room and efficiency.The method balances the inconsistency of design quality and efficiency.By comparing the results of a typical airfoil op-timization using the proposed method and the traditional Hicks-Henne model function method, feasibility and high efficiency of this method is verified.%研究了基本 Bezier 样条曲线的特性，对比了不同阶次 Bezier 曲线对超临界翼型的几何描述能力以及由几何偏差带来的气动性能的偏差。利用 Bezier 曲线的特性提出逐次升阶的翼型参数化方法，结合改进的粒子群优化算法，建立了逐步扩展设计空间的气动优化设计方法，兼顾设计空间和优化效率，很好地解决了设计质量和设计效率之间的矛盾。最后通过典型翼型的优化设计，对比了文中方法与传统 Hicks-Henne 型函数方法，验证了文中方法的可行性和高效性。
Lee, Chia-Yen; Wang, Hao-Jen; Lai, Jhih-Hao; Chang, Yeun-Chung; Huang, Chiun-Sheng
2017-02-01
Long-term comparisons of infrared image can facilitate the assessment of breast cancer tissue growth and early tumor detection, in which longitudinal infrared image registration is a necessary step. However, it is hard to keep markers attached on a body surface for weeks, and rather difficult to detect anatomic fiducial markers and match them in the infrared image during registration process. The proposed study, automatic longitudinal infrared registration algorithm, develops an automatic vascular intersection detection method and establishes feature descriptors by shape context to achieve robust matching, as well as to obtain control points for the deformation model. In addition, competitive winner-guided mechanism is developed for optimal corresponding. The proposed algorithm is evaluated in two ways. Results show that the algorithm can quickly lead to accurate image registration and that the effectiveness is superior to manual registration with a mean error being 0.91 pixels. These findings demonstrate that the proposed registration algorithm is reasonably accurate and provide a novel method of extracting a greater amount of useful data from infrared images.
Kasimova, R G; Tishin, D; Obnosov, Yu V; Dlussky, G M; Baksht, F B; Kacimov, A R
2014-08-21
Sizes, shapes, ambient and in-dome temperature, incoming solar radiation and illumination are measured on a Formica rufa anthill in a mixed forest of the Volga-Kama National Reserve in Russia. These data are used in a conceptual model of insolation of a right conical surface by direct-beam, descending atmospheric and ascending ground-reflected radiation. Unlike a standard calculation of the energy flux intercepted by a solar panel, the anthill is a 3-D structure and double-integration of the cosine of the angle between the solar beams and normal to the surface is carried out for a "cozy trapezium", where the insects expose themselves and the brood to "morning" sunbathing pulses (Jones and Oldroyd, 2007). Several constructal design problems are formulated with the criteria involving either a pure solar energy gained by the dome or this energy, as a mathematical criterion, penalized by additive terms of mechanical energy (potential and friction) lost by the ants in their diurnal forays from a "heartland" of the nest to the sun-basking zone on the surface. The unique and global optima are analytically found, with the optimal tilt angle of the cone explicitly expressed through the zenith angle of the Sun and meteorological constants for the isotropic sky model.
Variable volume combustor with aerodynamic support struts
Energy Technology Data Exchange (ETDEWEB)
Ostebee, Heath Michael; Johnson, Thomas Edward; Stewart, Jason Thurman; Keener, Christopher Paul
2017-03-07
The present application provides a combustor for use with a gas turbine engine. The combustor may include a number of micro-mixer fuel nozzles and a fuel injection system for providing a flow of fuel to the micro-mixer fuel nozzles. The fuel injection system may include a number of support struts supporting the fuel nozzles and providing the flow of fuel therethrough. The support struts may include an aerodynamic contoured shape so as to distribute evenly a flow of air to the micro-mixer fuel nozzles.
Optimum Shape Design Using Automatic Differentiation in Reverse Mode
Hafez, M.; Mohammadi, B.; Pironneau, O.
1996-01-01
This paper shows how to use automatic differentiation in reverse mode as a powerful tool in optimization procedures. It is also shown that for aerodynamic applications the gradients have to be as accurate as possible. In particular, the effect of having the exact gradient of he first or second order spatial discretization schemes is presented. We show that the loss of precision in the gradient affects not only the convergence, but also the final shape. Both two and three dimensional configurations of transonic and supersonic flows have been investigated. These cases involve up to several thousand control parameters.
Hansen, Martin O L
2015-01-01
Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its third edition, it has been substantially updated with respect to structural dynamics and control. The new control chapter now includes details on how to design a classical pitch and torque regulator to control rotational speed and power, while the section on structural dynamics has been extended with a simplified mechanical system explaining the phenomena of forward and backward whirling modes. Readers will also benefit from a new chapter on Vertical Axis W
Directory of Open Access Journals (Sweden)
yiping wang
2014-01-01
Full Text Available The numerical simulation and wind tunnel experiment were employed to investigate the aerodynamic characteristics of three typical rear shapes: fastback, notchback and squareback. The object was to investigate the sensibility of aerodynamic characteristic to the rear shape, and provide more comprehensive experimental data as a reference to validate the numerical simulation. In the wind tunnel experiments, the aerodynamic six components of the three models with the yaw angles range from -15 and 15 were measured. The realizable k-ε model was employed to compute the aerodynamic drag, lift and surface pressure distribution at a zero yaw angle. In order to improve the calculation efficiency and accuracy, a hybrid Tetrahedron-Hexahedron-Pentahedral-Prism mesh strategy was used to discretize the computational domain. The computational results showed a good agreement with the experimental data and the results revealed that different rear shapes would induce very different aerodynamic characteristic, and it was difficult to determine the best shape. For example, the fastback would obtain very low aerodynamic drag, but it would induce positive lift which was not conducive to stability at high speed, and it also would induce bad crosswind stability. In order to reveal the internal connection between the aerodynamic drag and wake vortices, the turbulent kinetic, recirculation length, position of vortex core and velocity profile in the wake were investigated by numerical simulation and PIV experiment.
Zahm, A F
1924-01-01
This report gives the description and the use of a specially designed aerodynamic plane table. For the accurate and expeditious geometrical measurement of models in an aerodynamic laboratory, and for miscellaneous truing operations, there is frequent need for a specially equipped plan table. For example, one may have to measure truly to 0.001 inch the offsets of an airfoil at many parts of its surface. Or the offsets of a strut, airship hull, or other carefully formed figure may require exact calipering. Again, a complete airplane model may have to be adjusted for correct incidence at all parts of its surfaces or verified in those parts for conformance to specifications. Such work, if but occasional, may be done on a planing or milling machine; but if frequent, justifies the provision of a special table. For this reason it was found desirable in 1918 to make the table described in this report and to equip it with such gauges and measures as the work should require.
Mehta, R. D.
1985-01-01
Research data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.
Datsenko, I.; Lozovenko, O.; Minaiev, Yu
2016-09-01
In their recent paper, Wang and Su (2015 Eur. J. Phys. 36 055010) acquainted readers with a solution to a problem about the optimal shape of an object for generating a maximum gravity field at a given point in space. After applying the variational principal and the Euler-Lagrange equation they obtained the shape for two-, three- and arbitrary n-dimensional cases. We are convinced that the problem is interesting enough to consider it with students. In this Comment we will try to present an easier way to solve it for the three-dimensional space.
Aerodynamic Analysis of Morphing Blades
Harris, Caleb; Macphee, David; Carlisle, Madeline
2016-11-01
Interest in morphing blades has grown with applications for wind turbines and other aerodynamic blades. This passive control method has advantages over active control methods such as lower manufacturing and upkeep costs. This study has investigated the lift and drag forces on individual blades with experimental and computational analysis. The goal has been to show that these blades delay stall and provide larger lift-to-drag ratios at various angles of attack. Rigid and flexible airfoils were cast from polyurethane and silicone respectively, then lift and drag forces were collected from a load cell during 2-D testing in a wind tunnel. Experimental data was used to validate computational models in OpenFOAM. A finite volume fluid-structure-interaction solver was used to model the flexible blade in fluid flow. Preliminary results indicate delay in stall and larger lift-to-drag ratios by maintaining more optimal angles of attack when flexing. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.
Discrete vortex method simulations of aerodynamic admittance in bridge aerodynamics
DEFF Research Database (Denmark)
Rasmussen, Johannes Tophøj; Hejlesen, Mads Mølholm; Larsen, Allan;
, and to determine aerodynamic forces and the corresponding ﬂutter limit. A simulation of the three-dimensional bridge responseto turbulent wind is carried out by quasi steady theory by modelling the bridge girder as a line like structure [2], applying the aerodynamic load coefﬁcients found from the current version...... of DVMFLOW in a strip wise fashion. Neglecting the aerodynamic admittance, i.e. the correlation of the instantaneous lift force to the turbulent ﬂuctuations in the vertical velocities, leads to higher response to high frequency atmospheric turbulence than would be obtained from wind tunnel tests....
Institute of Scientific and Technical Information of China (English)
闫晓磊; 钟志华; 张义; 孙光永
2012-01-01
To overcome the shortcoming that the calculation efficiency of the ordinary method is low in the flywheel rotor shape optimization, adopting the optimal control theory, brief analytic expressions of the optimal rotor shapes are gained directly based on analyzing the effects of rotating speed on the rotor shapes and dividing it into low, medium and high speed intervals. Through comparing the optimal shapes of the isotropic solid and hollow rotors at low, medium and high speed respectively, variations of the shapes with the rotating speed are revealed. The results indicate that at low rotating speed, the optimal shape of the flywheel rotor has a characteristic of "inner thin, outer thick" along the radial direction, at medium rotating speed, the optimal shape is "inner thick, outer thin", and at high rotating speed, it is "inner and outer thick, middle thin". At low rotating speed, the optimal shapes of the solid and hollow rotors are similar. However, at medium and high rotating speed, the hollow rotor optimal shape does not have constant stress arc as well as the one of the solid rotor. Because of containing the constant stress arc in the optimal shape, the solid rotor energy storage performance is better than the hollow one.%为克服飞轮转子形状优化时一般优化方法效率低的缺点,在分析角速度对转子形状影响的基础上,将转子角速度划分为低速、中速和高速三个阶段,采用最优控制理论,直接得到实心和空心飞轮转子的最优形状解析表达式.通过比较实心和空心转子低速、中速和高速情况下的最优形状,揭示飞轮转子最优形状随角速度变化的规律.研究结果表明,低角速度下,转子的最优形状沿半径方向“内薄外厚”;高角速度下,“内厚外薄”；中等角速度下,“两端厚中间薄”.低角速度情况下,实心和空心转子的最优形状相同;但中、高速情况下,实心转子的最优形状中包含等应力弧
Multidisciplinary design optimization of adaptive wing leading edge
Institute of Scientific and Technical Information of China (English)
SUN; RuJie; CHEN; GuoPing; ZHOU; Chen; ZHOU; LanWei; JIANG; JinHui
2013-01-01
Adaptive wing can significantly enhance aircraft aerodynamic performance, which refers to aerodynamic and structural opti-mization designs. This paper introduces a two-step approach to solve the interrelated problems of the adaptive leading edge. In the first step, the procedure of airfoil optimization is carried out with an initial configuration of NACA 0006. On the basis of the combination of design of experiment (DOE), response surface method (RSM) and genetic algorithm (GA), an adaptive air-foil can be obtained whose lift-to-drag ratio is larger than the baseline airfoil’s at the given angle of attack and subsonic speed.The next step is to design a compliant structure to achieve the target airfoil shape, which is the optimization result of the previous step. In order to minimize the deviation of the deformed shape from the target shape, the load path representation topology method is presented. This method is developed by way of GA, with size and shape optimization incorporated in it simul-taneously. Finally, a comparison study with the Solid Isotropic Material with Penalization (SIMP) method in Altair OptiStruct is conducted, and the results demonstrate the validity and effectiveness of the proposed approach.
Does an active adjustment of aerodynamic drag make sense?
Maciejewski, Marek
2016-09-01
The article concerns evaluation of the possible impact of the gap between the tractor and semitrailer on the aerodynamic drag coefficient. The aim here is not to adjust this distance depending on the geometrical shape of the tractor and trailer, but depending solely on the speed of articulated vehicle. All the tests have form of numerical simulations. The method of simulation is briefly explained in the article. It considers various issues such as the range and objects of tests as well as the test conditions. The initial (pre-adaptive) and final (after adaptation process) computational meshes have been presented as illustrations. Some of the results have been presented in the form of run chart showing the change of value of aerodynamic drag coefficients in time, for different geometric configurations defined by a clearance gap between the tractor and semitrailer. The basis for a detailed analysis and conclusions were the averaged (in time) aerodynamic drag coefficients as a function of the clearance gap.
Introduction to transonic aerodynamics
Vos, Roelof
2015-01-01
Written to teach students the nature of transonic flow and its mathematical foundation, this book offers a much-needed introduction to transonic aerodynamics. The authors present a quantitative and qualitative assessment of subsonic, supersonic, and transonic flow around bodies in two and three dimensions. The book reviews the governing equations and explores their applications and limitations as employed in modeling and computational fluid dynamics. Some concepts, such as shock and expansion theory, are examined from a numerical perspective. Others, including shock-boundary-layer interaction, are discussed from a qualitative point of view. The book includes 60 examples and more than 200 practice problems. The authors also offer analytical methods such as Method of Characteristics (MOC) that allow readers to practice with the subject matter. The result is a wealth of insight into transonic flow phenomena and their impact on aircraft design, including compressibility effects, shock and expansion waves, sho...
Aerodynamics of Small Vehicles
Mueller, Thomas J.
In this review we describe the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies, including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful ornithopter are also described.
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver
Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its third edition, it has been substantially updated with respect to structural dynamics and control. The new control chapter now includes details on how to design...... Turbines (VAWT). Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element Momentum method...... is also covered, as are eigenmodes and the dynamic behaviour of a turbine. The book describes the effects of the dynamics and how this can be modelled in an aeroelastic code, which is widely used in the design and verification of modern wind turbines. Furthermore, it examines how to calculate...
Wind Turbines Wake Aerodynamics
DEFF Research Database (Denmark)
Vermeer, L.; Sørensen, Jens Nørkær; Crespo, A.
2003-01-01
The aerodynamics of horizontal axis wind turbine wakes is studied. The contents is directed towards the physics of power extraction by wind turbines and reviews both the near and the far wake region. For the near wake, the survey is restricted to uniform, steady and parallel flow conditions......, thereby excluding wind shear, wind speed and rotor setting changes and yawed conditions. The emphasis is put on measurements in controlled conditions.For the far wake, the survey focusses on both single turbines and wind farm effects, and the experimental and numerical work are reviewed; the main interest...... is to study how the far wake decays downstream, in order to estimate the effect produced in downstream turbines.The article is further restricted to horizontal axis wind turbines and excludes all other types of turbines....
Wrona, Stanislaw; Pawelczyk, Marek
2016-03-01
An ability to shape frequency response of a vibrating plate according to precisely defined demands has a very high practical potential. It can be applied to improve acoustic radiation of the plate for required frequencies or enhance acoustic isolation of noise barriers and device casings by using both passive and active control. The proposed method is based on mounting severaladditional ribs and masses (passive and/or active) to the plate surface at locations followed from an optimization process. This paper, Part I, concerns derivation of a mathematical model of the plate with attached elements in the function of their shape and placement. The model is validated by means of simulations and laboratory experiments, and compared with models known from the literature. This paper is followed by a companion paper, Part II, where the optimization process is described. It includes arrangement of passive elements as well as actuators and sensors to improve controllability and observability measures, if active control is concerned.